Battery anode active material with fluorine resin coating

ABSTRACT

Battery anode active material with fluorine resin coating. A terminal of the fluorine resin is a hydroxyl group or the like capable of being fixed (for example, being absorbed or bound) on the surface of the anode active material layer (anode active material).

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.12/262,301 filed Oct. 31, 2008, now U.S. Pat. No. 8,932,756 issued Jan.13, 2015, the entirety of which is incorporated herein by reference tothe extent permitted by law. The present invention contains subjectmatter related to Japanese Patent Application JP 2007-283080 filed inthe Japanese Patent Office on Oct. 31, 2008, the entire contents ofwhich being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an anode having an anode activematerial layer on an anode current collector and a battery including theanode.

2. Description of the Related Art

In recent years, portable electronic devices such as combination cameras(videotape recorder), mobile phones, and notebook personal computershave been widely used, and it is strongly demanded to reduce their sizeand weight and to achieve their long life. Accordingly, as a powersource for the portable electronic devices, a battery, in particular alight-weight secondary batter capable of providing a high energy densityhas been developed.

Specially, a secondary battery using insertion and extraction of lithiumfor charge and discharge reaction (so-called lithium ion secondarybattery) is extremely prospective, since such a secondary battery canprovide a higher energy density compared to a lead battery and a nickelcadmium battery. The lithium ion secondary battery has a cathode, ananode, and an electrolytic solution. The anode has an anode activematerial layer on an anode current collector.

As an anode active material contained in the anode active materiallayer, a carbon material such as graphite has been widely used. Inrecent years, as the high performance and the multi functions of theportable electronic devices are developed, further improvement of thebattery capacity is demanded. Thus, it has been considered to usesilicon, tin or the like instead of the carbon material. Since thetheoretical capacity of silicon (4199 mAh/g) and the theoreticalcapacity of tin (994 mAh/g) are significantly higher than thetheoretical capacity of graphite (372 mAh/g), it is prospected that thebattery capacity is thereby highly improved.

However, in the case where silicon or the like is used as the anodeactive material, the anode active material inserting lithium whencharged is highly activated. Thus, the electrolytic solution is easilydecomposed, and lithium is easily inactivated. Thereby, the dischargecapacity is lowered when charge and discharge are repeated, and thussufficient cycle characteristics are hardly obtained.

Therefore, in the case where silicon or the like is used as the anodeactive material, various devices have been invented as well to improvethe cycle characteristics. Specifically, a technique that perfluoropolyether is contained in the electrolytic solution (for example, referto Japanese Unexamined Patent Application Publication Nos. 2002-305023and 2006-269374), and a technique that a coat containing perfluoropolyether is provided on the surface of an anode (for example, refer toJapanese Unexamined Patent Application Publication No. 2004-265609) havebeen proposed. In addition, a technique that an anode is covered with apolymer material such as a homopolymer or a copolymer of vinylidenefluoride (for example, refer to Japanese Unexamined Patent ApplicationPublication No. 2006-517719) has been proposed.

SUMMARY OF THE INVENTION

In these years, the high performance and the multi functions of theportable electronic devices are increasingly developed, and the electricpower consumption tends to be increased. Accordingly, charge anddischarge of the secondary battery are frequently repeated, and thus thecycle characteristics tend to be easily lowered. Therefore, furtherimprovement of the cycle characteristics of the secondary battery hasbeen aspired.

In view of the foregoing, in the invention, it is desirable to providean anode and a battery capable of improving the cycle characteristics.

According to an embodiment of the invention, there is provided an anodeincluding a coat on an anode active material layer provided on an anodecurrent collector, wherein the coat contains at least one selected fromthe group consisting of fluorine resins having a structure shown inChemical formula 1 or Chemical formula 2.

O—CF₂—CF₂

_(h)

O—CF₂

_(k)  Chemical formula 1(h and k represent a ratio, and h+k is 1.)

(m and n represent a ratio, and m+n is 1.)

According to an embodiment of the invention, there is provided a batteryincluding a cathode and an anode opposed to each other with a separatorin between and an electrolytic solution, wherein at least one of thecathode, the anode, the separator, and the electrolytic solutioncontains at least one selected from the group consisting of fluorineresins having a structure shown in Chemical formula 1 or Chemicalformula 2.

O—CF₂—CF₂

_(h)

O—CF₂

_(k)  Chemical formula 1(h and k represent a ratio, and h+k is 1.)

(m and n represent a ratio, and m+n is 1.)

According to the anode of the embodiment of the invention, since thecoat provided on the anode active material layer contains at least oneselected from the group consisting of the fluorine resins having thestructure shown in Chemical formula 1 or Chemical formula 2, theelectrochemical stability is improved. The same is applied to a casethat at least one of the cathode, the anode, the separator, and theelectrolytic solution contains at least one selected from the groupconsisting of the fluorine resins having the structure shown in Chemicalformula 1 or Chemical formula 2 in the battery of the embodiment of theinvention. Thereby, according to the battery of the embodiment of theinvention, decomposition reaction of the electrolytic solution can beprevented even when charge and discharge are repeated. As a result, thecycle characteristics can be improved.

Other and further objects, features and advantages of the invention willappear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section showing a structure of an anode according toan embodiment of the invention;

FIGS. 2A and 2B are an SEM photograph showing a cross sectionalstructure of the anode shown in FIG. 1 and a schematic drawing thereof;

FIGS. 3A and 3B are an SEM photograph showing another cross sectionalstructure of the anode shown in FIG. 1 and a schematic drawing thereof;

FIG. 4 is a cross section showing a structure of a first batteryincluding the anode according to the embodiment of the invention;

FIG. 5 is a cross section taken along line V-V of the first batteryshown in FIG. 4;

FIG. 6 is a cross section showing an enlarged part of the batteryelement shown in FIG. 5;

FIG. 7 is a cross section showing a structure of a second batteryincluding the anode according to the embodiment of the invention;

FIG. 8 is a cross section showing an enlarged part of the spirally woundelectrode body shown in FIG. 7;

FIG. 9 is a cross section showing a structure of a third batteryincluding the anode according to the embodiment of the invention;

FIG. 10 is a cross section taken along line X-X of the spirally woundelectrode body shown in FIG. 9;

FIG. 11 is a cross section showing an enlarged part of the spirallywound electrode body shown in FIG. 10;

FIG. 12 is an SEM photograph showing a surface structure of an anode inExample 1-1;

FIG. 13 is an SEM photograph showing a surface structure of an anode inExample 1-5;

FIG. 14 is a diagram showing a correlation between an oxygen content inan anode active material and a discharge capacity retention ratio;

FIG. 15 is a diagram showing a correlation between the number of thesecond oxygen-containing regions and a discharge capacity retentionratio;

FIG. 16 is a diagram showing a correlation between ten points averageheight of roughness profile of the surface of the anode currentcollector and a discharge capacity retention ratio; and

FIG. 17 is a diagram showing a correlation between a molar ratio and adischarge capacity retention ratio.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the invention will be hereinafter described in detailwith reference to the drawings.

FIG. 1 shows a cross sectional structure of an anode according to anembodiment of the invention. The anode is used, for example, for anelectrochemical device such as a battery. The anode has an anode currentcollector 1 having a pair of faces, an anode active material layer 2provided on the anode current collector 1, and a coat 3 provided on theanode active material layer 2.

The anode current collector 1 is preferably made of a metal materialhaving favorable electrochemical stability, favorable electricconductivity, and favorable mechanical strength. As such a metalmaterial, for example, copper (Cu), nickel (Ni), stainless or the likeis cited. Specially, copper is preferable since a high electricconductivity can be thereby obtained.

In particular, the foregoing metal material preferably contains one ormore metal elements not forming an intermetallic compound with anelectrode reactant. When the intermetallic compound is formed with theelectrode reactant, lowering of the current collectivity characteristicsand separation of the anode active material layer 2 from the anodecurrent collector 1 may occur, being affected by a stress due toexpansion and shrinkage of the anode active material layer 2 while theelectrochemical device is operated (for example, when a battery ischarged and discharged). As the foregoing metal element, for example,copper, nickel, titanium (Ti), iron (Fe), chromium (Cr) or the like iscited.

The foregoing metal material preferably contains one or more metalelements being alloyed with the anode active material layer 2. Thereby,the contact characteristics between the anode current collector 1 andthe anode active material layer 2 are improved, and thus the anodeactive material layer 2 is hardly separated from the anode currentcollector 1. As a metal element that does not form an intermetalliccompound with the electrode reactant and is alloyed with the anodeactive material layer 2, for example, in the case that the anode activematerial layer 2 contains silicon as an anode active material, copper,nickel, iron or the like is cited. These metal elements are preferablein terms of the strength and the electric conductivity.

The anode current collector 1 may have a single layer structure or amultilayer structure. In the case where the anode current collector 1has the multilayer structure, it is preferable that the layer adjacentto the anode active material layer 2 is made of a metal material beingalloyed with the anode active material layer 2, and layers not adjacentto the anode active material layer 2 are made of other metal material.

The surface of the anode current collector 1 is preferably roughened.Thereby, due to the so-called anchor effect, the contact characteristicsbetween the anode current collector 1 and the anode active materiallayer 2 are improved. In this case, it is enough that at least thesurface of the anode current collector 1 in the region opposed to theanode active material layer 2 is roughened. As a roughening method, forexample, a method of forming fine particles by electrolytic treatmentand the like are cited. The electrolytic treatment is a method ofproviding concavity and convexity by forming fine particles on thesurface of the anode current collector 1 by electrolytic method in anelectrolytic bath. A copper foil provided with the electrolytictreatment is generally called “electrolytic copper foil.”

Ten points average height of roughness profile Rz of the surface of theanode current collector 1 is not particularly limited, but is preferably1.5 μm or more and 6.5 μm or less, since thereby the contactcharacteristics between the anode current collector 1 and the anodeactive material layer 2 are further improved. More specifically, if theten points average height of roughness profile Rz is smaller than 1.5μm, there is a possibility that sufficient contact characteristics arenot able to be obtained. Meanwhile, if the ten points average height ofroughness profile Rz is larger than 6.5 μm, there is a possibility thatmany holes are included in the anode active material layer 2 and therebythe surface area is increased.

The anode active material layer 2 contains, as an anode active material,one or more anode materials capable of inserting and extracting anelectrode reactant, and may also contain other materials such as anelectrical conductor and a binder according to needs. The anode activematerial layer 2 may be provided on the both faces of the anode currentcollector 1, or may be provided on only a single face of the anodecurrent collector 1.

As the anode material capable of inserting and extracting the electrodereactant, for example, a material that is capable of inserting andextracting the electrode reactant and contains at least one of metalelements and metalloid elements as an element is cited. Such an anodematerial is preferably used, since a high energy density can be therebyobtained. Such an anode material may be a simple substance, an alloy, ora compound of a metal element or a metalloid element, or may have one ormore phases thereof at least in part. In the invention, “the alloy”includes an alloy containing one or more metal elements and one or moremetalloid elements, in addition to an alloy composed of two or moremetal elements. Further, “the alloy” may contain a nonmetallic element.The texture thereof includes a solid solution, a eutectic crystal(eutectic mixture), an intermetallic compound, and a texture in whichtwo or more thereof coexist.

As such a metal element or such a metalloid element, for example, ametal element or a metalloid element capable of forming an alloy withthe electrode reactant is cited. Specifically, magnesium (Mg), boron(B), aluminum (Al), gallium (Ga), indium (In), silicon, germanium (Ge),tin, lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc, hafnium(Hf), zirconium (Zr), yttrium (Y), palladium (Pd), platinum (Pt) and thelike are cited. Specially, at least one of silicon and tin is preferablyused, and silicon is more preferably used, since silicon and tin havethe high ability to insert and extract the electrode reactant, and thuscan provide a high energy density.

As the anode material containing at least one of silicon and tin, forexample, the simple substance, an alloy, or a compound of silicon; thesimple substance, an alloy, or a compound of tin; or a material havingone or more phases thereof at least in part is cited. Each thereof maybe used singly, or a plurality thereof may be used by mixture.

As the alloy of silicon, for example, an alloy containing at least oneselected from the group consisting of tin, nickel, copper, iron, cobalt,manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony(Sb), and chromium as the second element other than silicon is cited. Asthe compound of silicon, for example, a compound containing oxygen orcarbon (C) is cited, and the compound of silicon may contain theforegoing second element in addition to silicon. Examples of an alloy ora compound of silicon include SiB₄, SiB₆, Mg₂Si, Ni₂Si, TiSi₂, MoSi₂,CoSi₂, NiSi₂, CaSi₂, CrSi₂, Cu₅Si, FeSi₂, MnSi₂, NbSi₂, TaSi₂, VSi₂,WSi₂, ZnSi₂, SiC, Si₃N₄, Si₂N₂O, SiO_(v) (0<v≦2), SnO_(w) (0<w≦2), LiSiOand the like are cited.

As the alloy of tin, for example, an alloy containing at least oneselected from the group consisting of silicon, nickel, copper, iron,cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth,antimony, and chromium as the second element other than tin is cited. Asthe compound of tin, for example, a compound containing oxygen or carbonis cited, and may contain the foregoing second element in addition totin. Examples of an alloy or a compound of tin include SnSiO₃, LiSnO,Mg₂Sn and the like.

In particular, as the anode material containing at least one of siliconand tin, for example, an anode material containing the second elementand the third element in addition to tin as the first element ispreferable. As the second element, at least one selected from the groupconsisting of cobalt, iron, magnesium, titanium, vanadium (V), chromium,manganese, nickel, copper, zinc, gallium, zirconium, niobium (Nb),molybdenum, silver, indium, cerium (Ce), hafnium, tantalum (Ta),tungsten (W), bismuth, and silicon is cited. As the third element, atleast one selected from the group consisting of boron, carbon, aluminum,and phosphorus (P) is cited. In the case where the second element andthe third element are contained, the cycle characteristics are improved.

Specially, an SnCoC-containing material that contains tin, cobalt, andcarbon as an element in which the carbon content is 9.9 wt % or more and29.7 wt % or less, and the cobalt ratio to the total of tin and cobalt(Co/(Sn+Co)) is 30 wt % or more and 70 wt % or less is preferable. Insuch a composition range, a high energy density is obtained.

The SnCoC-containing material may further contain other elementaccording to needs. As other element, for example, silicon, iron,nickel, chromium, indium, niobium, germanium, titanium, molybdenum,aluminum, phosphorus, gallium, bismuth or the like is preferable. Two ormore thereof may be contained, since thereby higher effects areobtained.

The SnCoC-containing material has a phase containing tin, cobalt, andcarbon. Such a phase preferably has a low crystalline structure or anamorphous structure. Further, in the SnCoC-containing material, at leastpart of carbon as an element is preferably bonded to a metal element ora metalloid element as other element. Cohesion or crystallization of tinor the like is thereby prevented.

The SnCoC-containing material can be formed by, for example, mixing rawmaterials of each element, dissolving the resultant mixture in anelectric furnace, a high frequency induction furnace, an arc meltingfurnace or the like and then solidifying the resultant. Otherwise, theSnCoC-containing material can be formed by various atomization methodssuch as gas atomizing and water atomizing; various roll methods; or amethod using mechanochemical reaction such as mechanical alloying methodand mechanical milling method. Specially, the SnCoC-containing materialis preferably formed by the method using mechanochemical reaction, sincethereby the anode active material can have a low crystalline structureor an amorphous structure. For the method using the mechanochemicalreaction, for example, a manufacturing apparatus such as a planetaryball mill apparatus and an attliter is used.

As a measurement method for examining bonding state of elements, forexample, X-ray Photoelectron Spectroscopy (XPS) is used. In XPS, in thecase of graphite, the peak of is orbit of carbon (C1s) is observed at284.5 eV in the apparatus in which energy calibration is made so thatthe peak of 4f orbit of gold atom (Au4f) is obtained in 84.0 eV. In thecase of surface contamination carbon, the peak is observed at 284.8 eV.Meanwhile, in the case of higher electric charge density of carbonelement, for example, in the case where carbon is bonded to a metalelement or a metalloid element, the peak of C1s is observed in theregion lower than 284.5 eV. That is, in the case where the peak of thecomposite wave of C1s obtained for the SnCoC-containing material isobserved in the region lower than 284.5 eV, at least part of carboncontained in the SnCoC-containing material is bonded to the metalelement or the metalloid element as other element.

In XPS, for example, the peak of C1s is used for correcting the energyaxis of spectrums. Since surface contamination carbon generally existson the surface, the peak of C1s of the surface contamination carbon isset to in 284.8 eV, which is used as an energy reference. In XPS, thewaveform of the peak of C1s is obtained as a form including the peak ofthe surface contamination carbon and the peak of carbon in theSnCoC-containing material. Therefore, for example, by analyzing thewaveform with the use of commercially available software, the peak ofthe surface contamination carbon and the peak of carbon in theSnCoC-containing material are separated. In the analysis of thewaveform, the position of the main peak existing on the lowest boundenergy side is set to the energy reference (284.8 eV).

The anode active material layer 2 using the simple substance, an alloy,or a compound of silicon; the simple substance, an alloy, or a compoundof tin; or a material having one or more phases thereof at least in partas an anode material is formed by, for example, vapor-phase depositionmethod, liquid-phase deposition method, spraying method, coating method,firing method, or a combination of two or more of these methods. In thiscase, the anode current collector 1 and the anode active material layer2 are preferably alloyed in at least part of the interface thereof.Specifically, at the interface thereof, the element of the anode currentcollector 1 may be diffused in the anode active material layer 2; or theelement of the anode active material layer 2 may be diffused in theanode current collector 1; or these elements may be diffused in eachother. Thereby, destruction due to expansion and shrinkage of the anodeactive material layer 2 in charge and discharge is prevented, and theelectron conductivity between the anode current collector 1 and theanode active material layer 2 is improved.

As vapor-phase deposition method, for example, physical depositionmethod or chemical deposition method is cited. Specifically, vacuumevaporation method, sputtering method, ion plating method, laserablation method, thermal CVD (Chemical Vapor Deposition) method, plasmaCVD method and the like are cited. As liquid-phase deposition method, aknown technique such as electrolytic plating and electroless plating isused. Coating method is, for example, a method in which a particulateanode active material mixed with a binder or the like is dispersed in asolvent and the anode current collector is coated with the resultant.Firing method is, for example, a method in which the anode currentcollector is coated by coating method, and then heat treatment isprovided at a temperature higher than the melting point of the binder orthe like. For firing method, a known technique such as atmosphere firingmethod, reactive firing method, and hot press firing method is availableas well.

In addition to the foregoing anode material, as the anode materialcapable of inserting and extracting the electrode reactant, for example,a carbon material is cited. As the carbon material, for example,graphitizable carbon, non-graphitizable carbon in which the spacing of(002) plane is 0.37 nm or more, graphite in which the spacing of (002)plane is 0.34 nm or less and the like are cited. More specifically,pyrolytic carbons, coke, glassy carbon fiber, an organic polymercompound fired body, activated carbon, carbon black or the like iscited. Of the foregoing, the coke includes pitch coke, needle coke,petroleum coke and the like. The organic polymer compound fired body isobtained by firing and carbonizing a phenol resin, a furan resin or thelike at an appropriate temperature. In the carbon material, the crystalstructure change associated with insertion and extraction of theelectrode reactant is very little. Therefore, by using the carbonmaterial, a high energy density is obtained and superior cyclecharacteristics are obtained. In addition, the carbon material alsofunctions as an electrical conductor, and thus the carbon material ispreferably used. The shape of the carbon material may be any of afibrous shape, a spherical shape, a granular shape, and a scale-likeshape.

Further, as the anode material capable of inserting and extracting theelectrode reactant, for example, a metal oxide, a polymer compound andthe like capable of inserting and extracting the electrode reactant arecited. As the metal oxide, for example, iron oxide, ruthenium oxide,molybdenum oxide or the like is cited. As the polymer compound, forexample, polyacetylene, polyaniline, polypyrrole or the like is cited.

It is needless to say that as the anode material capable of insertingand extracting the electrode reactant, a material other than theforegoing may be used. Further, given two or more of the foregoingseries of anode materials capable of inserting and extracting theelectrode reactant may be used by mixture.

The anode active material preferably contains oxygen as an element,since thereby expansion and shrinkage of the anode active material layer2 are prevented. In the case where the anode active material hassilicon, at least part of oxygen is preferably bonded to part ofsilicon. The bonding state may be in the form of silicon monoxide,silicon dioxide, or in the form of other metastable state.

The oxygen content in the anode active material is preferably 3 atomic %or more and 40 atomic % or less, since thereby higher effects areobtained. Specifically, if the oxygen content is smaller than 3 atomic%, there is a possibility that expansion and shrinkage of the anodeactive material layer 2 are not sufficiently prevented. Meanwhile, ifthe oxygen content is larger than 40 atomic %, the resistance may beexcessively increased. In the case where the anode is used together withan electrolytic solution in an electrochemical device, the anode activematerial does not include a coat formed by decomposition of theelectrolytic solution and the like. That is, when the oxygen content inthe anode active material is calculated, oxygen in the foregoing coat isnot included in the calculation.

To make the anode active material contain oxygen, for example, oxygengas may be continuously introduced into a chamber when the anode activematerial is deposited by vapor-phase deposition method. In particular,when a desired oxygen content is not obtained only by introducing theoxygen gas, a liquid (for example, moisture vapor or the like) may beintroduced into the chamber as a supply source of oxygen.

Further, the anode active material preferably contains at least onemetal element selected from the group consisting of iron, cobalt,nickel, chromium, titanium, and molybdenum as an element. Thereby, thebinding characteristics of the anode active material are improved,expansion and shrinkage of the anode active material layer 2 areprevented, and resistance of the anode active material is lowered. Themetal element content in the anode active material can be voluntarilyset. However, in the case where the anode is used for a battery, anexcessively high content of the metal element is not practical, since insuch a case, the thickness of the anode active material layer 2 shouldbe increased to obtain a desired battery capacity, and therebyseparation of the anode active material layer 2 from the anode currentcollector 1 and break of the anode active material layer 2 may be easilycaused.

To make the anode active material contain the foregoing metal element,for example, when the anode active material is deposited by evaporationmethod as vapor-phase deposition method, an evaporation source mixedwith the metal element may be used, or multiple evaporation sources maybe used.

Further, it is preferable that the anode active material has anoxygen-containing region in which the anode active material has oxygenin the thickness direction, and the oxygen content in theoxygen-containing region is larger than the oxygen content in the otherregions. Thereby, expansion and shrinkage of the anode active materiallayer 2 are prevented. It is possible that the regions other than theoxygen-containing region contain oxygen or do not contain oxygen. It isneedless to say that when the regions other than the oxygen-containingregion also has oxygen, the oxygen content thereof is lower than theoxygen content in the oxygen-containing region.

In this case, to further suppress expansion and shrinkage of the anodeactive material layer 2, it is preferable that the regions other thanthe oxygen-containing region also have oxygen, and the anode activematerial includes a first oxygen-containing region (region having thelower oxygen content) and a second oxygen-containing region having thehigher oxygen content than that of the first oxygen-containing region(region having the higher oxygen content). In this case, it ispreferable that the second oxygen-containing region is sandwichedbetween the first oxygen-containing regions. It is more preferable thatthe first oxygen-containing region and the second oxygen-containingregion are alternately and repeatedly layered. Thereby, higher effectsare obtained. The oxygen content in the first oxygen-containing regionis preferably small as much as possible. The oxygen content in thesecond oxygen-containing region is, for example, similar to the oxygencontent in the case that the anode active material contains oxygendescribed above.

To make the anode active material include the first oxygen-containingregion and the second oxygen-containing region, for example, oxygen gasmay be by intermittently introduced into a chamber or the oxygen gasamount introduced into the chamber is changed when the anode activematerial is deposited by vapor-phase deposition method. It is needlessto say that when a desired oxygen content is not able to be obtainedonly by introducing the oxygen gas, liquid (for example, moisture vaporor the like) may be introduced into the chamber.

It is possible that the oxygen content of the first oxygen-containingregion is clearly different from the oxygen content of the secondoxygen-containing region, or the oxygen content of the firstoxygen-containing region is not clearly different from the oxygencontent of the second oxygen-containing region. In particular, in thecase where the introduction amount of the foregoing oxygen gas iscontinuously changed, the oxygen content may be continuously changed. Inthe case where the introduction amount of the oxygen gas isintermittently changed, the first oxygen-containing region and thesecond oxygen-containing region become so-called “layers.” Meanwhile, inthe case where the introduction amount of the oxygen gas is continuouslychanged, the first oxygen-containing region and the secondoxygen-containing region become “lamellar state” rather than “layers.”In the latter case, the oxygen content in the anode active material isdistributed in a state of ups and downs. In this case, it is preferablethat the oxygen content is incrementally or continuously changed betweenthe first oxygen-containing region and the second oxygen-containingregion. In the case where the oxygen content is changed drastically, theion diffusion characteristics may be lowered, or the resistance may beincreased.

In particular, the anode active material may be composed of a pluralityof particles. In the case where the anode active material is formed bydeposition method such as vapor-phase deposition method, the anodeactive material may have a single layer structure by being formedthrough a single deposition step, or may have a multilayer structure bybeing formed through a plurality of deposition steps. However, toprevent the anode current collector 1 from being damaged thermally whenthe anode active material is deposited by evaporation method or the likeassociated with high heat in the deposition step, the anode activematerial preferably has the multilayer structure. When the depositionstep of the anode active material is divided into several steps (theanode active material is sequentially formed and deposited), time thatthe anode current collector 1 is exposed at high heat is shortenedcompared to a case that the anode active material is formed through asingle deposition step.

Further, the anode active material is preferably linked to the anodecurrent collector 1, since thereby the contact strength of the anodeactive material layer 2 to the anode current collector 1 is increased.To link the anode active material with the anode current collector 1,for example, the anode active material is deposited on the anode currentcollector 1 by vapor-phase deposition method or the like, the anodeactive material is grown from the surface of the anode current collector1 in the thickness direction of the anode active material layer 2. Inthis case, it is preferable that the anode active material is depositedby vapor-phase deposition method, and the anode current collector 1 andthe anode active material layer 2 are alloyed in at least the interfacein between as described above.

In the case where the anode active material is composed of a pluralityof particles, the anode active material layer 2 preferably contains ametal material not being alloyed with the electrode reactant togetherwith the anode active material. Since each anode active material isbound to each other with the metal material in between, expansion andshrinkage of the anode active material layer 2 are prevented. In thiscase, in particular, when the anode active material is deposited byvapor-phase deposition method or the like, high binding characteristicsare obtained as well. The metal material has a metal element not beingalloyed with the electrode reactant. As the metal element, for example,at least one selected from the group consisting of iron, cobalt, nickel,zinc, and copper is cited. It is needless to say that the metal materialmay contain a metal element other than the foregoing metal elements.“Metal material” in the invention is a comprehensive term, and thus themetal material may be one of a simple substance, an alloy, and acompound, as long as the metal material contains a metal element notbeing alloyed with the electrode reactant.

Molar ratio M2/M1 between the number of moles M1 per unit area of theanode active material and the number of moles M2 per unit area of themetal material is not particularly limited, but preferably 1/15 or moreand 7/1 or less. Thereby, expansion and shrinkage of the anode activematerial layer 2 are more prevented.

A detailed structural of the anode will be described by taking anexample of a case in which the anode active material is composed of aplurality of particles and has a multilayer structure in the particlethereof.

FIGS. 2A and 2B show an enlarged partial cross sectional structure ofthe anode current collector 1 and the anode active material layer 2shown in FIG. 1. FIG. 2A is a scanning electron microscope (SEM)photograph (secondary electron image), and FIG. 2B is a schematicdrawing of the SEM image shown in FIG. 2A.

In the case where the anode active material is composed of a pluralityof particles (anode active material particles 201), a plurality of gapsand voids are generated in the anode active material layer 2. Morespecifically, on the roughened surface of the anode current collector 1,a plurality of projections (for example, fine particles formed byelectrolytic treatment) exist. In this case, the anode active materialis deposited several times on the surface of the anode current collector1 by deposition method such as vapor-phase deposition method to form alaminated body of the anode active material, and thereby the anodeactive material particles 201 are incrementally grown in the thicknessdirection for every projection mentioned above. According to the densitystructure, the multilayer structure, and the surface structure of theplurality of anode active material particles 201, a plurality of gaps202 and 203 and a plurality of voids 204 are generated.

The gap 202 is generated between each anode active material particle 201adjacent to each other as the anode active material particle 201 isgrown for every projection described above. The gap 203 is generatedbetween each layer as the anode active material particles 201 have themultilayer structure. As fibrous minute projections (not shown) aregenerated on the surface of the anode active material particles 201, thevoid 204 is generated between the projections. The void 204 may begenerated over the entire surface of the anode active material particles201, or may be generated in part thereof. The foregoing fibrous minuteprojection is generated on the surface of the anode active materialparticles 201 every time when the anode active material particles 201are formed. Thus, the void 204 is generated not only on the uppermostsurface (exposed face) of the anode active material particles 201, butalso between each layer.

FIGS. 3A and 3B show another cross sectional structure of the anodecurrent collector 1 and the anode active material layer 2, and show anSEM photograph and a schematic drawing corresponding to FIGS. 2A and 2B.

The anode active material layer 2 has a metal material 205 not beingalloyed with the foregoing electrode reactant in the gaps 202 and 203and the void 204. The plurality of anode active material particles 201are bound with the metal material 205 in between, and thereby expansionand shrinkage of the anode active material layer 2 are prevented. Inthis case, at least one of the gaps 202 and 203 and the void 204 mayhave the metal material 205, and specially all of the gaps 202 and 203and the void 204 preferably have the metal material 205, since therebyhigher effects are obtained.

The metal material 205 intrudes into the gap 202 between adjacent anodeactive material particles 201. More specifically, in the case where theanode active material particles 201 are formed by vapor-phase depositionmethod or the like, as described above, the anode active materialparticles 201 are grown for every projection existing on the surface ofthe anode current collector 1, and thus the gap 202 is generated betweenthe anode active material particles 201. The gap 202 causes lowering ofthe binding characteristics of the anode active material layer 2.Therefore, to improve the binding characteristics, the metal material205 fills in the foregoing gap 202. In this case, it is enough that partof the gap 202 is filled therewith, but the larger filling amount ispreferable, since thereby the binding characteristics of the anodeactive material layer 2 are further improved. The filling amount of themetal material 205 is preferably 20% or more, more preferably 40% ormore, and much more preferably 80% or more.

The metal material 205 intrudes into the gap 203 in the anode activematerial particles 201. More specifically, in the case where the anodeactive material particles 201 have the multilayer structure, the gap 203is generated between each layer. The gap 203 causes lowering of thebinding characteristics of the anode active material layer 2 as theforegoing gap 202 does. Therefore, to improve the bindingcharacteristics, the metal material 205 fills in the foregoing gap 203.In this case, it is enough that part of the gap is filled therewith, butthe larger filling amount is preferable, since thereby the bindingcharacteristics of the anode active material layer 2 are furtherimproved.

Further, to prevent the fibrous minute projection (not shown) generatedon the exposed face of the uppermost layer of the anode active materialparticles 201 from adversely affecting the performance of anelectrochemical device, the projection is covered with the metalmaterial 205. More specifically, in the case where the anode activematerial particles 201 are formed by vapor-phase deposition method orthe like, the fibrous minute projections are generated on the surfacethereof, and thus the void 204 is generated between the projections. Thevoid 204 causes increase of the surface area of the anode activematerial, and accordingly the amount of an irreversible coat formed onthe surface is also increased, possibly resulting in lowering ofprogression of the electrode reaction. Therefore, to avoid the loweringof progression of the electrode reaction, the foregoing void 204 isfilled with the metal material 205. In this case, it is enough atminimum that part of the void 204 is filled therewith, but the largerfilling amount is preferable, since thereby the lowering of progressionof the electrode reaction is more prevented. A state that the metalmaterial 205 is dotted on the exposed face (uppermost face) of the anodeactive material particles 221 means that the foregoing minute projectionexists in the location where the metal material 205 is dotted. It isneedless to say that the metal material 205 is not necessarily dotted onthe surface of the anode active material particles 201, but may coverthe entire surface thereof.

The metal material 205 that intrudes into the gap 203 has a function tofill in the void 204 in each layer. More specifically, in the case wherethe anode active material is deposited several times, the foregoingminute projection is generated on the surface thereof for everydeposition. Therefore, the metal material 205 fills in not only the gap203 in each layer, but also the void 204 in each layer.

The metal material 205 is formed by, for example, at least one ofvapor-phase deposition method and liquid-phase deposition method.Specially, the metal material 205 is preferably formed by liquid-phasedeposition method. Thereby, the metal material 205 easily intrudes intothe gaps 202 and 203 and the void 204. As vapor-phase deposition method,for example, a method similar to the method of forming the anode activematerial is cited. Further, as liquid-phase deposition method, forexample, plating method such as electrolytic plating method andelectroless plating method are cited. Specially, electrolytic platingmethod is preferable, since thereby the metal material 205 more easilyintrudes into the gaps 202 and 203 and the void 204.

In particular, the metal material 205 preferably has crystallinity,since thereby resistance of the entire anode is lowered, and theelectrode reactant is easily inserted and extracted in the anodecompared to a case that the metal material 205 does not havecrystallinity (amorphous state). Further, in this case, the electrodereactant is uniformly inserted and extracted in initial operation of anelectrochemical device (for example, in initial charge of a battery),and local stress is hardly generated in the anode, and accordingly awrinkle is prevented from being generated.

In FIGS. 2A and 2B and 3A and 3B, the description has been given of acase that the anode active material has the multilayer structure, andthe both gaps 202 and 203 exist in the anode active material layer 2,and thus the anode active material layer 2 has the metal material 205 inthe gaps 202 and 203. Meanwhile, in the case where the anode activematerial has a single layer structure, and only the gap 202 exists inthe anode active material layer 2, the anode active material layer 2 hasthe metal material 205 only in the gap 202. It is needless to say thatin the both cases, since the void 204 exists in the anode activematerial layer 2, the anode active material layer 2 has the metalmaterial 205 in the void 204.

As the electrical conductor, for example, a carbon material such asgraphite, carbon black, acetylene black, and Ketjen black is cited. Sucha carbon material may be used singly, or a plurality thereof may be usedby mixture. The electrical conductor may be a metal material, a polymeror the like as long as the material has the electric conductivity.

As the binder, for example, a synthetic rubber such as styrene-butadienerubber, fluorinated rubber, and ethylene propylene diene; or a polymermaterial such as polyvinylidene fluoride is cited. One thereof may beused singly, or a plurality thereof may be used by mixture.

The coat 3 contains at least one selected from the group consisting offluorine resins having the structure shown in Chemical formula 1 orChemical formula 2 (hereinafter simply referred to as “fluorine resin”).When the fluorine resin having the structure shown in Chemical formula 1or Chemical formula 2 is provided on the anode active material layer 2as a coat, the chemical stability of the anode is thereby improved. Thecoat 3 may be provided on the both faces of the anode current collector1, or may be provided on only a single face. The structure of thefluorine resin can be identified by, for example, examining elementbonding state in the coat 3 with the use of XPS.

O—CF₂—CF₂

_(h)

O—CF₂

_(k)  Chemical formula 1(h and k represent a ratio, and h+k is 1.)

(m and n represent a ratio, and m+n is 1.)

The ratio between h and k (h:k) shown in Chemical formula 1 can bevoluntarily set. Specially, h>k is preferable, since thereby thechemical stability of the coat 3 is thereby further improved. The sameis similarly applied to the ratio between m and n shown in Chemicalformula 2.

The fluorine resin may have any structure as a whole as long as thefluorine resin has the structure shown in Chemical formula 1 or Chemicalformula 2. That is, a terminal of the fluorine resin may be a perfluorogroup such as a perfluoroalkyl group, or may be any of other variousgroups. When a terminal of the fluorine resin is the perfluoroalkylgroup, the fluorine resin is so-called perfluoropolyether. As theperfluoroalkyl group, for example, a trifluoromethyl group (—CF₃) or thelike is cited. However, a perfluoroalkyl group other than thetrifluoromethyl group may be cited as well.

In particular, the fluorine resin preferably has the structure shown inChemical formula 3 as a whole. In this case, the fluorine resin is fixedon the surface of the anode active material layer 2 (anode activematerial) through R1 and R2 at the terminals. Thus, contact strength ofthe coat 3 to the anode active material layer 2 is increased compared toa case that a terminal thereof is a perfluoro group. In this case, theanode active material preferably contains at least one selected from thegroup consisting of the simple substance, an alloy, and a compound ofsilicon, and the simple substance, an alloy, and a compound of tin.Thereby, the fluorine resin is firmly fixed on the surface of the anodeactive material, and thus contact strength of the coat 3 is moreincreased.R1-X—R2  Chemical formula 3(X is a structure shown in Chemical formula 1 or Chemical formula 2. Atleast one of R1 and R2 is a group capable of being fixed on the surfaceof the anode active material layer.)

At least one of R1 and R2 shown in Chemical formula 3 may be any group,as long as the group can be fixed on the surface of the anode activematerial. “To be fixed” means a state that interaction (contact force)between the anode active material and the coat 3 is increased comparedto a case that a terminal thereof is a perfluoroalkyl group. Such astate includes, for example, absorption, binding, adhesion or the like.

As at least one of R1 and R2, for example, a hydroxyl group (—OH), anester group (—COOR), a silane group (—SiR₃), an alkoxysilane group(—Si(OR)₃), a phosphate group (—H₂PO₄), an amino group (—NR₂), an amidegroup (—CONR₂), a cyano group (—CC≡N), an isocyanate group (—N═C═O) orthe like is cited, since thereby contact strength of the coat 3 isincreased. R in the foregoing respective groups may be any group as longas it is a monovalent group such as a hydrogen group and an alkyl group.

More specifically, at least one of R1 and R2 has the structure shown inChemical formula 4. When p in Chemical formula 4 is 0 or 1, an oxo group(—O—) is included in some cases, and is not included in some cases. Thesame is applied to R3 (q) and R4 (r). R7 and R8 in Chemical formula 11may be identical or different. The same is applied to R9 to R18 shown inChemical formulas 12 to 14 and Chemical formula 16.

O

_(p)

R3

_(q)

R4

_(r)R5  Chemical formula 4(p, q, and r are 0 or 1. R3 is a divalent linked group shown in Chemicalformula 5, R4 is a divalent linked group shown in Chemical formula 6 orChemical formula 7, and R5 is a monovalent group shown in Chemicalformula 8 to Chemical formula 17.)

CF₂

_(n)  Chemical formula 5(n is one of integer numbers 1 or higher.)

CH₂

_(n)  Chemical formula 6(n is one of integer numbers 1 or higher.)

O—CH₂—CH₂

_(n)OH  Chemical formula 8

(n is one of integer numbers 0 to 10.)

(R6 is a hydrogen group, an alkyl group having a carbon number of 10 orless, or —CH₂—CN.)

(R7 and R8 are a hydrogen group or an alkyl group having a carbon numberof 20 or less.)

(R9 to R11 are a hydrogen group, a halogen group, an alkyl group havinga carbon number of 10 or less, an alkylene group having a carbon numberof 10 or less, or an alkoxyl group having a carbon number of 10 orless.)

(R12 and R13 are a hydrogen group, a hydroxyl group, a halogen group, oran alkyl group having a carbon number of 10 or less.)

(R14 and R15 are a hydrogen group or an alkyl group having a carbonnumber of 10 or less.)

(R16 to R18 are a hydrogen group or a halogen group.)—C≡N  Chemical formula 17

Specially, the structure shown in Chemical formula 8 or Chemical formula9 or the structure shown in Chemical formula 12 (in the case that R9 toR11 are an alkoxyl group) is preferable, and the structure shown inChemical formula 12 is more preferable, since thereby higher effects areobtained. The reason why the carbon number is limited in Chemicalformula 8 and Chemical formula 10 to Chemical formula 14 is as follows.If the carbon number is excessively large, solubility into a solvent orthe like becomes low. In this case, when the coat 3 is formed byliquid-phase deposition method such as dipping method, the formationamount (coating amount) is hardly controlled in a good reproduciblefashion.

As a specific example of R1 and R2 shown in Chemical formula 3 andChemical formula 4, for example, the group shown in Chemical formula18(1) to Chemical formula 20(7) is cited.

The relation between the structure shown in Chemical formula 4(structure shown in Chemical formula 5 to Chemical formula 17) and theseries of groups shown in Chemical formula 18(1) to Chemical formula20(7) will be described as follows.

The groups shown in Chemical formulas 18(1) to 18(4) are groups in whichp, q, and r are 0, and R5 is Chemical formula 12 (R9 to R11 are analkoxyl group).

The group shown in Chemical formula 19(1) is a group in which p and qare 0, r is 1, R4 is Chemical formula 6 (n is 1), and R5 is Chemicalformula 8 (n is 0). The group shown in Chemical formula 19(2) is a groupin which p and q are 0, r is 1, R4 is Chemical formula 6 (n is 1), andR5 is Chemical formula 8 (n is 2). The group shown in Chemical formula19(3) is a group in which p and q are 0, r is 1, R4 is Chemical formula6 (n is 1), and R5 is Chemical formula 9. The group shown in Chemicalformula 19(4) is a group in which p, q, and r are 0, and R5 is Chemicalformula 10 (R6 is a methyl group). The group shown in Chemical formula19(5) is a group in which p and q are 0, r is 1, R4 is Chemical formula6 (n is 1), and R5 is Chemical formula 13 (R12 and R13 is a hydrogengroup). The group shown in Chemical formula 19(6) is a group in which pand q are 0, r is 1, R4 is Chemical formula 7, and R5 is Chemicalformula 8 (n is 0). The group shown in Chemical formula 19(7) is a groupin which p, q, and r are 0, and R5 is Chemical formula 11 (R7 and R8 area hydrogen group).

The group shown in Chemical formula 20(1) is a group in which p, q, andr are 0, and R5 is Chemical formula 11 (R7 is a hydrogen group, and R8is an octadecyl group). The group shown in Chemical formula 20(2) is agroup in which p and q are 0, r is 1, R4 is Chemical formula 6 (n is 1),and R5 is Chemical formula 14 (R14 and R15 are a hydrogen group). Thegroup shown in Chemical formula 20(3) is a group in which p and q are 0,r is 1, R4 is Chemical formula 6 (n is 1), and R5 is Chemical formula15. The group shown in Chemical formula 20(4) is a group in which p, q,r are 0, and R5 is Chemical formula 10 (R6 is —CH₂—CN). The group shownin Chemical formula 20(5) is a group in which p and r are 1, q is 0, R4is Chemical formula 6 (n is 1), and R5 is Chemical formula 17. The groupshown in Chemical formula 20(6) is a group in which p and r are 0, q is1, R3 is Chemical formula 5 (n is 1), and R5 is Chemical formula 8 (n is0). The group shown in Chemical formula 20(7) is a group in which p andq are 0, r is 1, R4 is Chemical formula 6 (n is 1), and R5 is Chemicalformula 16 (R16 to R18 are a hydrogen group).

Specially, a fluorine resin having the structure shown in Chemicalformulas 18(1) to 18(4) or Chemical formulas 19(1) to 19(3) ispreferable, and a fluorine resin having the structure shown in Chemicalformulas 18(1) to 18(4) is more preferable, since the electrode reactantis hardly consumed due to existence of the coat 3 in electrode reactionand thus electrode reaction efficiency is improved.

The coat 3 can be formed by, for example, dipping method, coatingmethod, spray method or the like. Specifically, liquid-phase depositionmethod represented by dipping method is preferable, since the coat 3having a sufficient film thickness can be easily formed. However, thecoat 3 may be formed by other method.

In particular, when the coat 3 containing the fluorine resin is providedon the anode active material layer 2, the surface of the coat 3preferably has a fluoride of the electrode reactant (hereinafter simplyreferred to as “fluoride”). The fluoride prevents expansion andshrinkage of the anode active material layer 2 and keeps the surfacearea of the anode active material small. Thus, the chemical stability ofthe anode is further improved. The fluoride is formed by reactionbetween the electrode reactant and fluorine in the fluorine resin inelectrode reaction (for example, in charge and discharge in a battery).For example, in the case where the anode is used for a batterycontaining lithium as an electrode reactant, the fluoride includeslithium fluoride. The fluoride may be formed on the surface of the coat3 in a state of a membrane or in a state of particles.

In the case where the fluoride is formed on the surface of the coat 3,there is a tendency that formation of the fluoride is almost completedin one electrode reaction (first electrode reaction), and the fluorideis almost never formed through subsequent electrode reactions (on andafter the second electrode reaction). Accordingly, if the fluoride isgenerated on the surface of the coat 3, it is possible to determinewhether or not electrode reaction is initiated in the anode withoutrelation to the history of the anode (the number of electrode reactionsrepeated in the anode until then). In other words, when the fluoride isgenerated on the surface of the coat 3, it means that electrode reactionhas been already generated in the anode. The foregoing “one electrodereaction” means, in the case of charge and discharge when the anode isused for a battery, a case that the battery is charged and discharged ina general (practical) conditions, but does not mean a case that thebattery is charged and discharged under special conditions such asovercharge.

The anode is formed, for example, by the following procedure.

First, the anode current collector 1 made of an electrolytic copper foilor the like is prepared. After that, the anode active material isdeposited on the surface of the anode current collector 1 by vapor-phasedeposition method or the like to form the anode active material layer 2.When the anode active material is deposited by vapor-phase depositionmethod, it is possible to form a single layer structure by 1 depositionstep, or a multilayer structure by a plurality of deposition steps. Inparticular, in the case where the anode active material is formed intothe multilayer structure, it is possible that the anode active materialis deposited a plurality of times while the anode current collector 1 isrelatively reciprocated to an evaporation source, or it is possible thatthe anode active material is deposited a plurality of times while ashutter is repeatedly opened and closed keeping the anode currentcollector 1 fixed to the evaporation source. Finally, a solution inwhich a fluorine resin is dissolved in a solvent or the like isprepared. After that, the anode current collector 1 on which the anodeactive material layer 2 is formed is dipped into the solution, taken outand dried to form the coat 3. Thereby, the anode is completed.

According to the anode, the coat 3 provided on the anode active materiallayer 2 contains at least one selected from the fluorine resins havingthe structure shown in Chemical formula 1 or Chemical formula 2. Thus,compared to a case that the coat 3 is not provided, the chemicalstability of the anode is improved. Such an action is particularlysignificant when the anode active material contains highly activesilicon or tin. As a result, the anode contributes to improvement of thecycle characteristics of an electrochemical device using the anode.

In particular, when the fluorine resin has the structure shown inChemical formula 3, more particularly, when the fluorine resin has thestructure that the terminal of the fluorine resin (R1, R2) is a hydroxylgroup or the like, or when the fluorine resin has the structure shown inChemical formula 4, the contact strength of the coat 3 to the anodeactive material layer 2 is increased, and thus higher effects areobtained, compared to a case that a terminal is a perfluoro alkyl group.

Further, when the fluoride of the electrode reactant exists on thesurface of the coat 3, the chemical stability of the anode is furtherimproved, and thus higher effects are obtained.

Further, when the anode active material has oxygen and the oxygencontent in the anode active material is 3 atomic % or more and 40 atomic% or less, or when the anode active material contains at least one metalelement selected from the group consisting of iron, cobalt, nickel,titanium, chromium, and molybdenum, or when the anode active materialhas the oxygen-containing region (region in which oxygen exists and theoxygen content thereof is higher than that of the other regions) in thethickness direction, higher effects are obtained.

Further, when the ten points average height of roughness profile Rz ofthe surface of the anode current collector 1 is 1.5 μm or more and 6.5μm or less, the contact characteristics between the anode currentcollector 1 and the anode active material layer 2 are improved, andtherefore higher effects are obtained.

In addition, when the anode active material layer 2 has the metalmaterial not being alloyed with the electrode reactant together with theanode active material, the binding characteristics of the anode activematerial are improved and expansion and shrinkage of the anode activematerial layer 2 are prevented, and thus higher effects are obtained. Inthis case, when the metal material is formed by liquid-phase depositionmethod, higher effects are obtained. Further, when the molar ratio M2/M1between the anode active material and the metal material is 1/15 or moreand 7/1 or less, higher effects are obtained.

Next, a description will be hereinafter given of a usage example of theforegoing anode. As an example of the electrochemical devices, batteriesare herein taken. The anode is used for the batteries as follows.

The battery herein described, for example, includes a cathode and theanode opposed to each other with a separator in between, and anelectrolytic solution. The battery is a lithium-ion secondary battery inwhich the anode capacity is expressed based on insertion and extractionof lithium as an electrode reactant. The cathode has a cathode activematerial layer on a cathode current collector. The electrolytic solutioncontains a solvent and an electrolyte salt.

In the secondary battery, at least one element out of the cathode, theanode, the separator, and the electrolytic solution contains at leastone selected from the fluorine resins having the structure shown inChemical formula 1 or Chemical formula 2. Accordingly, the chemicalstability of the element containing the fluorine resin is improved, andthus decomposition reaction of the electrolytic solution is prevented.In the case where the cathode and the anode contains the fluorine resin,as already described for the foregoing anode, a coat containing thefluorine resin is provided on the cathode active material layer or theanode active material layer. In the case where the electrolytic solutioncontains the fluorine resin, the fluorine resin is dispersed in thesolvent. In this case, the entire fluorine resin may be dissolved in thesolvent, or only part thereof may be dissolved therein. In the casewhere the separator has the fluorine resin, a coat containing thefluorine resin is provided on a single face or the both faces thereof.

The element containing the fluorine resin may be only one of thecathode, the anode, the separator, and the electrolytic solution.However, it is preferable that two of the cathode, the anode, theseparator, and the electrolytic solution contain the fluorine resin, andit is more preferable that all thereof contain the fluorine resin, sincethereby decomposition reaction of the electrolytic solution is moreprevented. Specially, when limited to a combination composed of twoelements containing the fluorine resin, the combination of the anode andthe separator is preferable, since thereby higher effects are obtained.

In the case where only one of the cathode, the anode, the separator, andthe electrolytic solution contains the fluorine resin, it is preferablethat the cathode, the anode, or the separator contains the fluorineresin, and it is more preferable that the anode contains the fluorineresin, since thereby the decomposition reaction is more prevented.

The secondary battery type (battery structure) is not particularlylimited. A description will be hereinafter given of a structure of thesecondary battery in detail for a case that the anode contains thefluorine resin taking a square secondary battery, a cylindricalsecondary battery, and a laminated film secondary battery as an exampleof a battery structure.

First Battery

FIG. 4 and FIG. 5 show cross sectional structures of a first battery.FIG. 5 shows a cross section taken along line V-V shown in FIG. 4.

The battery is, as described above, a lithium ion secondary battery inwhich the capacity of an anode 22 is expressed based on insertion andextraction of lithium as an electrode reactant. In the secondarybattery, a battery element 20 having a flat spirally wound structure ismainly contained in a battery can 11. The battery can 11 is, forexample, a square package member. As shown in FIG. 5, the square packagemember has a shape with the cross section in the longitudinal directionof a rectangle or an approximate rectangle (including curved lines inpart). The square package member structures not only a square battery inthe shape of a rectangle, but also a square battery in the shape of anoval. That is, the square package member means a rectangle vessel-likemember with the bottom or an oval vessel-like member with the bottom,which respectively has an opening in the shape of a rectangle or in theshape of an approximate rectangle (oval shape) formed by connectingcircular arcs by straight lines. FIG. 5 shows a case that the batterycan 11 has a rectangular cross sectional shape. The battery structureincluding the battery can 11 is called square structure.

The battery can 11 is made of, for example, a metal material containingiron, aluminum (Al), or an alloy thereof. The battery can 11 may have afunction as an anode terminal as well. In this case, to prevent thesecondary battery from being swollen by using the rigidity (hardlydeformable characteristics) of the battery can 11 when charged anddischarged, rigid iron is more preferable than aluminum. In the casewhere the battery can 11 is made of iron, the iron may be plated bynickel (Ni) or the like, for example.

The battery can 11 has a hollow structure in which one end of thebattery can 11 is closed and the other end of the battery can 11 isopened. At the open end of the battery can 11, an insulating plate 12and a battery cover 13 are attached, and thereby inside of the batterycan 11 is hermetically closed. The insulating plate 12 is locatedbetween the battery element 20 and the battery cover 13, is arrangedperpendicularly to the spirally wound circumferential face of thebattery element 20, and is made of, for example, polypropylene or thelike. The battery cover 13 is, for example, made of a material similarto that of the battery can 11, and also has a function as an anodeterminal as the battery can 11 does.

Outside of the battery cover 13, a terminal plate 14 as a cathodeterminal is provided. The terminal plate 14 is electrically insulatedfrom the battery cover 13 with an insulating case 16 in between. Theinsulating case 16 is made of, for example, polybutylene terephthalateor the like. In the approximate center of the battery cover 13, athrough-hole is provided. A cathode pin 15 is inserted in thethrough-hole so that the cathode pin is electrically connected to theterminal plate 14 and is electrically insulated from the battery cover13 with a gasket 17 in between. The gasket 17 is made of, for example,an insulating material, and the surface thereof is coated with asphalt.

In the vicinity of the rim of the battery cover 13, a cleavage valve 18and an injection hole 19 are provided. The cleavage valve 18 iselectrically connected to the battery cover 13. When the internalpressure of the battery becomes a certain level or more by internalshort circuit, external heating or the like, the cleavage valve 18 isseparated from the battery cover 13 to release the internal pressure.The injection hole 19 is sealed by a sealing member 19A made of, forexample, a stainless corundum.

The battery element 20 is formed by layering a cathode 21 and the anode22 with a separator 23 in between and then spirally winding theresultant laminated body. The battery element 20 is flat according tothe shape of the battery can 11. A cathode lead 24 made of aluminum orthe like is attached to an end of the cathode 21 (for example, theinternal end thereof). An anode lead 25 made of nickel or the like isattached to an end of the anode 22 (for example, the outer end thereof).The cathode lead 24 is electrically connected to the terminal plate 14by being welded to an end of the cathode pin 15. The anode lead 25 iswelded and electrically connected to the battery can 11.

FIG. 6 shows an enlarged part of the spirally wound electrode body 20shown in FIG. 5. In the cathode 21, for example, a cathode activematerial layer 21B is provided on the both faces of a strip-shapedcathode current collector 21A having a pair of faces. The cathode activematerial layer 21B may be provided on the both faces of the cathodecurrent collector 21A or on only a single face of the cathode currentcollector 21A. The cathode current collector 21A is, for example, madeof a metal material such as aluminum, nickel, and stainless. The cathodeactive material layer 21B contains, as a cathode active material, one ormore cathode materials capable of inserting and extracting lithium. Thecathode active material layer 21B may contain other material such as abinder and an electrical conductor according to needs. Details of thebinder and the electrical conductor are similar to those of the casedescribed for the foregoing anode.

As the cathode material capable of inserting and extracting lithium, forexample, lithium-containing compounds are preferable, since thereby ahigh energy density is obtained. As the lithium-containing compound, forexample, a complex oxide containing lithium and a transition metalelement or a phosphate compound containing lithium and a transitionmetal element is cited. In particular, a compound containing at leastone selected from the group consisting of cobalt, nickel, manganese, andiron as a transition metal element is preferable, since thereby a highervoltage is obtained. The chemical formula thereof is expressed as, forexample, Li_(x)M1O₂ or Li_(y)M2PO₄. In the formula, M1 and M2 representone or more transition metal elements. Values of x and y vary accordingto the charge and discharge state of the battery, and are generally inthe range of 0.05≦x≦1.10 and 0.05≦y≦1.10.

As the complex oxide containing lithium and a transition metal element,for example, a lithium cobalt complex oxide (Li_(x)CoO₂), a lithiumnickel complex oxide (Li_(x)NiO₂), a lithium nickel cobalt complex oxide(Li_(x)Ni_(1-z)CO_(z)O₂ (z<1)), a lithium nickel cobalt manganesecomplex oxide (Li_(x)Ni_((1-v-w))CO_(v)Mn_(w)O₂) (v+w<1)), lithiummanganese complex oxide having a spinel structure (LiMn₂O₄) or the likeis cited. Specially, a complex oxide containing cobalt is preferable,since thereby a high capacity is obtained and superior cyclecharacteristics are obtained. As the phosphate compound containinglithium and a transition metal element, for example, lithium ironphosphate compound (LiFePO₄), a lithium iron manganese phosphatecompound (LiFe_(1-u)Mn_(u)PO₄ (u<1)) or the like is cited.

In addition, as the foregoing cathode material, for example, an oxidesuch as titanium oxide, vanadium oxide, and manganese dioxide; adisulfide such as titanium disulfide and molybdenum sulfide; achalcogenide such as niobium selenide; sulfur; a conductive polymer suchas polyaniline and polythiophene are cited.

The anode 22 has a structure similar to that of the anode describedabove. For example, in the anode 22, an anode active material layer 22Band a coat 22C are provided on the both faces of a strip-shaped anodecurrent collector 22A having a pair of faces. The structures of theanode current collector 22A, the anode active material layer 22B, andthe coat 22C are respectively similar to the structures of the anodecurrent collector 1, the anode active material layer 2, and the coat 3in the anode described above. In the anode 22, the charge capacity ofthe anode active material capable of inserting and extracting lithium ispreferably larger than the charge capacity of the cathode 21.

The separator 23 separates the cathode 21 from the anode 22, and passesions as an electrode reactant while preventing current short circuit dueto contact of the both electrodes. The separator 23 is made of, forexample, a porous film made of a synthetic resin such aspolytetrafluoroethylene, polypropylene, and polyethylene, a ceramicporous film or the like. The separator 23 may have a structure in whichtwo or more porous films as the foregoing porous films are layered.

An electrolytic solution as a liquid electrolyte is impregnated in theseparator 23. The electrolytic solution contains, for example, a solventand an electrolyte salt dissolved therein.

The solvent contains, for example, one or more nonaqueous solvents suchas an organic solvent. The nonaqueous solvents include, for example, anester carbonate solvent such as ethylene carbonate, propylene carbonate,butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methylcarbonate, and methyl propyl carbonate. Thereby, superior capacitycharacteristics, superior cycle characteristics, and superior storagecharacteristics are obtained. Specially, a mixture of a high viscositysolvent such as ethylene carbonate and propylene carbonate and a lowviscosity solvent such as dimethyl carbonate, ethyl methyl carbonate,and diethyl carbonate is preferable. Thereby, the dissociation propertyof the electrolyte salt and the ion mobility are improved, and thushigher effects are obtained.

The solvent preferably contains at least one of a chain ester carbonatehaving halogen as an element shown in Chemical formula 21 and a cyclicester carbonate having halogen as an element shown in Chemical formula22. Thereby, a stable protective film (coat) is formed on the surface ofthe anode 22 and decomposition reaction of the electrolytic solution isprevented, and thus the cycle characteristics are improved.

(R21 to R26 are a hydrogen group, a halogen group, an alkyl group, or analkyl halide group. At least one of R21 to R26 is the halogen group orthe alkyl halide group.)

(R31 to R34 are a hydrogen group, a halogen group, an alkyl group, or analkyl halide group. At least one of R31 to R34 is the halogen group orthe alkyl halide group.)

R21 to R26 in Chemical formula 21 may be identical or different. Thesame is applied to R31 to R34 in Chemical formula 22. “Alkyl halidegroup” described in R21 to R24 and R31 to R34 is a group obtained bysubstituting at least partial hydrogen of the alkyl group with halogen.The halogen type is not particularly limited, but for example, at leastone selected from the group consisting of fluorine, chlorine, andbromine is cited. Specially, fluorine is preferable, since therebyhigher effects are obtained. It is needless to say that other halogenmay be used.

The number of halogen is more preferably two than one, and further maybe three or more, since thereby an ability to form the protective filmis improved and more rigid and stable protective film is formed.Accordingly, decomposition reaction of the electrolytic solution is moreprevented.

As the chain ester carbonate having halogen shown in Chemical formula21, for example, fluoromethyl methyl carbonate, bis (fluoromethyl)carbonate, difluoromethyl methyl carbonate or the like is cited. Onethereof may be used singly, or a plurality thereof may be used bymixture.

As the cyclic ester carbonate having halogen shown in Chemical formula22, for example, the compounds shown in Chemical formulas 23-1 to 24-9are cited. That is, 4-fluoro-1,3-dioxolane-2-one of Chemical formula23(1), 4-chloro-1,3-dioxolane-2-one of Chemical formula 23(2),4,5-difluoro-1,3-dioxolane-2-one of Chemical formula 23(3),tetrafluoro-1,3-dioxolane-2-one of Chemical formula 23(4),4-fluoro-5-chloro-1,3-dioxolane-2-one of Chemical formula 23(5),4,5-dichloro-1,3-dioxolane-2-one of Chemical formula 23(6),tetrachloro-1,3-dioxolane 2-one of Chemical formula 23(7), 4,5-bistrifluoro methyl-1,3-dioxolane 2-one of Chemical formula 23(8),4-trifluoro methyl-1,3-dioxolane-2-one of Chemical formula 23(9),4,5-difluoro-4,5-dimethyl-1,3-dioxolane-2-one of Chemical formula23(1)0, 4-methyl-5,5-difluoro-1,3-dioxolane-2-one of Chemical formula23(1)1, 4-ethyl-5,5-difluoro-1,3-dioxolane-2-one of Chemical formula23(1)2 and the like are cited. Further,4-trifluoromethyl-5-fluoro-1,3-dioxolane-2-one of Chemical formula24(1), 4-trifluoromethyl-5-methyl-1,3-dioxolane-2-one of Chemicalformula 24(2), 4-fluoro-4,5-dimethyl-1,3-dioxolane-2-one of Chemicalformula 24(3), 4,4-difluoro-5-(1,1-difluoroethyl)-1,3-dioxolane-2-one ofChemical formula 24(4), 4,5-dichloro-4,5-dimethyl-1,3-dioxolane-2-one ofChemical formula 24(5), 4-ethyl-5-fluoro-1,3-dioxolane-2-one of Chemicalformula 24(6), 4-ethyl-4,5-difluoro-1,3-dioxolane-2-one of Chemicalformula 24(7), 4-ethyl-4,5,5-trifluoro-1,3-dioxolane-2-one of Chemicalformula 24(8), 4-fluoro-4-methyl-1,3-dioxolane-2-one of Chemical formula24(9) and the like are cited. One thereof may be used singly, or aplurality thereof may be used by mixture.

Specially, 4-fluoro-1,3-dioxolane-2-one or4,5-difluoro-1,3-dioxolane-2-one is preferable, and4,5-difluoro-1,3-dioxolane-2-one is more preferable. In particular, as4,5-difluoro-1,3-dioxolane-2-one, a trans isomer is more preferable thana cis isomer, since the trans isomer is easily available and provideshigh effects.

Further, the solvent preferably contains a cyclic ester carbonate havingan unsaturated bond, since thereby the cycle characteristics can beimproved. As the cyclic ester carbonate having an unsaturated bond, forexample, vinylene carbonate, vinyl ethylene carbonate or the like iscited. A plurality thereof may be used by mixture.

Further, the solvent preferably contains sultone (cyclic estersulfonate), since thereby the cycle characteristics are improved andswollenness of the secondary battery is prevented. As the sultone, forexample, propane sultone, propene sultone or the like is cited. Aplurality thereof may be used by mixture.

In addition, the solvent preferably contains an acid anhydride, sincethereby the cycle characteristics are improved. As the acid anhydride,for example, succinic anhydride, glutaric anhydride, maleic anhydride,sulfobenzoic acid anhydride, sulfo propionic acid anhydride, sulfobutyric acid anhydride, ethane disulfonic acid anhydride, propanedisulfonic acid anhydride, benzene disulfonic acid anhydride and thelike are cited. A plurality thereof may be used by mixture. Specially,sulfo benzoic acid anhydride or sulfo propionic acid anhydride ispreferable, since thereby sufficient effects are obtained. The contentof the acid anhydride in the solvent is, for example, 0.5 wt % or moreand 3 wt % or less.

The electrolyte salt contains, for example, one or more light metalsalts such as a lithium salt. As the lithium salt, for example, lithiumhexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate,lithium hexafluoroarsenate or the like is cited, since thereby superiorcapacity characteristics, superior cycle characteristics, and superiorstorage characteristics are obtained. Specially, lithiumhexafluorophosphate is preferable, since the internal resistance islowered, and thus higher effects are obtained.

The electrolyte salt preferably contains at least one selected from thegroup consisting of the compounds shown in Chemical formula 25 toChemical formula 27. Thereby, in the case where such a compound is usedtogether with the foregoing lithium hexafluorophosphate or the like,higher effects are obtained. R41 and R43 in Chemical formula 25 may beidentical or different. The same is applied to R51 to R53 in Chemicalformula 26 and R61 and R62 in Chemical formula 27.

(X41 is a Group 1A element or a Group 2A element in the short periodperiodic table or aluminum. M41 is a transition metal, a Group 3Belement, a Group 4B element, or a Group 5B element in the short periodperiodic table. R41 is a halogen group. Y41 is —OC—R42-CO—, —OC—CR43₂-,or —OC—CO—. R42 is an alkylene group, an alkylene halide group, anarylene group, or an arylene halide group. R43 is an alkyl group, analkyl halide group, an aryl group, or an aryl halide group. a4 is one ofinteger numbers 1 to 4. b4 is one of integer numbers 0, 2, and 4. c4,d4, m4, and n4 is one of integer numbers 1 to 3.)

(X51 is a Group 1A element or a Group 2A element in the short periodperiodic table. M51 is a transition metal element, a Group 3B element, aGroup 4B element, or a Group 5B element in the short period periodictable. Y51 is —OC—(CR51₂)_(b5)-CO—, —R53₂C—(CR52₂)_(c5)-CO—,—R53₂C—(CR52₂)_(c5)-CR53₂-, —R53₂C—(CR52₂)_(c5)-SO₂—,—O₂S—(CR52₂)_(d5)-SO₂—, or —OC—(CR52₂)_(d5)-SO₂—. R51 and R53 are ahydrogen group, an alkyl group, a halogen group, or an alkyl halidegroup. At least one of R51/R53 is respectively the halogen group or thealkyl halide group. R52 is a hydrogen group, an alkyl group, a halogengroup, or an alkyl halide group. a5, e5, and n5 are an integer number of1 or 2. b5 and d5 are one of integer numbers 1 to 4. c5 is one ofinteger numbers 0 to 4. f5 and m5 are one of integer numbers 1 to 3.)

(X61 is a Group 1A element or a Group 2A element in the short periodperiodic table. M61 is a transition metal element, a Group 3B element, aGroup 4B element, or a Group 5B element in the short period periodictable. Rf is a fluorinated alkyl group with the carbon number in therange from 1 to 10 or a fluorinated aryl group with the carbon number inthe range from 1 to 10. Y61 is —OC—(CR61₂)_(d6)-CO—,—R62₂C—(CR61₂)_(d6)-CO—, —R62₂C—(CR61₂)_(d6)-CR62₂-,—R62₂C—(CR61₂)_(d6)-SO₂—, —O₂S—(CR61₂)_(e6)-SO₂—, or—OC—(CR61₂)_(e6)-SO₂—. R61 is a hydrogen group, an alkyl group, ahalogen group, or an alkyl halide group. R62 is a hydrogen group, analkyl group, a halogen group, or an alkyl halide group, and at least onethereof is the halogen group or the alkyl halide group. a6, f6, and n6are an integer number of 1 or 2. b6, c6, and e6 are one of integernumbers 1 to 4. d6 is one of integer numbers 0 to 4. g6 and m6 are oneof integer numbers 1 to 3.)

As a compound shown in Chemical formula 25, for example, the compoundsshown in Chemical formulas 28-1 to 28-6 are cited. As a compound shownin Chemical formula 26, for example, the compounds shown in Chemicalformulas 29-1 to 29-8 are cited. As a compound shown in Chemical formula27, for example, the compound shown in Chemical formula 30 or the likeis cited. It is needless to say that the compound is not limited to thecompounds shown in Chemical formula 28(1) to Chemical formula 30, andthe compound may be other compound as long as such a compound has thestructure shown in Chemical formula 25 to Chemical formula 27.

The electrolyte salt may contain at least one selected from the groupconsisting of the compounds shown in Chemical formula 31 to Chemicalformula 33. Thereby, in the case where such a compound is used togetherwith the foregoing lithium hexafluorophosphate, higher effects areobtained. m and n in Chemical formula 31 may be identical or different.The same is applied to p, q, and r in Chemical formula 33.LiN(C_(m)F_(2m+1)SO₂)(C_(n)F_(2n+1)SO₂)  Chemical formula 31

(m and n are an integer number of 1 or more.)

(R71 is a straight chain/branched perfluoro alkylene group with thecarbon number in the range from 2 to 4.)LiC(C_(p)F_(2p+1)SO₂)(C_(q)F_(2q+1)SO₂)(C_(r)F_(2r+1)SO₂)  Chemicalformula 33

(p, q, and r are an integer number of 1 or more.)

As the chain compound shown in Chemical formula 31, for example, lithiumbis(trifluoromethanesulfonyl)imide (LiN(CF₃SO₂)₂), lithiumbis(pentafluoroethanesulfonyl)imide (LiN(C₂F₅SO₂)₂), lithium(trifluoromethanesulfonyl) (pentafluoroethanesulfonyl)imide(LiN(CF₃SO₂)(C₂F₅SO₂)), lithium (trifluoromethanesulfonyl)(heptafluoropropanesulfonyl)imide (LiN(CF₃SO₂)(C₃F₇SO₂)), lithium(trifluoromethanesulfonyl) (nonafluorobutanesulfonyl)imide(LiN(CF₃SO₂)(C₄F₉SO₂)) or the like is cited. One thereof may be usedsingly, or a plurality thereof may be used by mixture.

As the cyclic compound shown in Chemical formula 32, for example, thecompounds shown in Chemical formulas 34-1 to 34-4 are cited. That is,lithium 1,2-perfluoroethanedisulfonylimide shown in Chemical formula34-1, lithium 1,3-perfluoropropanedisulfonylimide shown in Chemicalformula 34-2, lithium 1,3-perfluorobutanedisulfonylimide shown inChemical formula 34-3, lithium 1,4-perfluorobutanedisulfonylimide shownin Chemical formula 34-4 or the like is cited. One thereof may be usedsingly, or a plurality thereof may be used by mixture. Specially,lithium 1,2-perfluoroethanedisulfonylimide is preferable, since therebysufficient effects are obtained.

As the chain compound shown in Chemical formula 33, for example, lithiumtris(trifluoro methane sulfonyl)methyde (LiC(CF₃SO₂)₃) or the like iscited.

The content of the electrolyte salt to the solvent is preferably 0.3mol/kg or more and 3.0 mol/kg or less. If out of the foregoing range,there is a possibility that the ion conductivity is significantlylowered.

The secondary battery is manufactured, for example, by the followingprocedure.

First, the cathode 21 is formed. First, a cathode active material, abinder, and an electrical conductor are mixed to prepare a cathodemixture, which is dispersed in an organic solvent to form paste cathodemixture slurry. Subsequently, the both faces of the cathode currentcollector 21A are uniformly coated with the cathode mixture slurry by adoctor blade, a bar coater or the like, which is dried. Finally, thecoating is compression-molded by a rolling press machine or the likewhile being heated if necessary to form the cathode active materiallayer 21B. In this case, the coating may be compression-molded overseveral times.

Further, the anode 22 is formed by forming the anode active materiallayer 22B and the coat 22C on the both faces of the anode currentcollector 22A by the same procedure as that of forming the anodedescribed above.

Next, the battery element 20 is formed by using the cathode 21 and theanode 22. First, the cathode lead 24 is attached to the cathode currentcollector 21A by welding or the like, and the anode lead 25 is attachedto the anode current collector 22A by welding or the like. Subsequently,the cathode 21 and the anode 22 are layered with the separator 23 inbetween, and spirally wound in the longitudinal direction. Finally, aspirally wound body is shaped in the flat shape.

The secondary battery is assembled as follows. First, after the batteryelement 20 is contained in the battery can 11, the insulating plate 12is arranged on the battery element 20. Subsequently, the cathode lead 24is connected to the cathode pin 15 by welding or the like, and the anodelead 25 is connected to the battery can 11 by welding or the like. Afterthat, the battery cover 13 is fixed on the open end of the battery can11 by laser welding or the like. Finally, the electrolytic solution isinjected into the battery can 11 from the injection hole 19, andimpregnated in the separator 23. After that, the injection hole 19 issealed by the sealing member 19A. The secondary battery shown in FIG. 4to FIG. 6 is thereby completed.

In the secondary battery, when charged, for example, lithium ions areextracted from the cathode 21, and are inserted in the anode 22 throughthe electrolytic solution impregnated in the separator 23. Meanwhile,when discharged, for example, lithium ions are extracted from the anode22, and are inserted in the cathode 21 through the electrolytic solutionimpregnated in the separator 23.

According to the square secondary battery, since the anode 22 has thestructure similar to that of the foregoing anode, decomposition reactionof the electrolytic solution is prevented even when charge and dischargeare repeated. Accordingly, the cycle characteristics can be improved. Inthis case, when the anode 22 contains silicon advantageous for obtaininga high capacity, the cycle characteristics are improved. Thus, highereffects can be thereby obtained than in a case in which the anodecontains other anode material such as a carbon material.

In particular, when the battery can 11 is made of a rigid metal, theanode 22 is hardly damaged when the anode active material layer 22B isexpanded and shrunk compared to a case that the battery can is made of asoft film. Therefore, the cycle characteristics can be further improved.In this case, when the battery can 11 is made of iron that is more rigidthan aluminum, higher effects are obtained.

Effects of the secondary battery other than the foregoing effects aresimilar to those of the foregoing anode.

Second Battery

FIG. 7 and FIG. 8 show a cross sectional structure of a second battery.FIG. 8 shows an enlarged part of a spirally wound electrode body 40shown in FIG. 7. The battery is a lithium ion secondary battery in whichthe capacity of an anode 42 is expressed based on insertion andextraction of lithium as an electrode reactant as described above. Thebattery mainly contains the spirally wound electrode body 40 in which acathode 41 and the anode 42 are spirally wound with a separator 43 inbetween, and a pair of insulating plates 32 and 33 inside a battery can31 in the shape of an approximately hollow cylinder. The batterystructure including the battery can 31 is a so-called cylindricalsecondary battery.

The battery can 31 is made of, for example, a metal material similar tothat of the battery can 11 in the foregoing first battery. One end ofthe battery can 31 is closed, and the other end thereof is opened. Thepair of insulating plates 32 and 33 is arranged to sandwich the spirallywound electrode body 40 in between and to extend perpendicularly to thespirally wound periphery face.

At the open end of the battery can 31, a battery cover 34, and a safetyvalve mechanism 35 and a PTC (Positive Temperature Coefficient) device36 provided inside the battery cover 34 are attached by being caulkedwith a gasket 37. Inside of the battery can 31 is thereby hermeticallysealed. The battery cover 34 is made of, for example, a material similarto that of the battery can 31. The safety valve mechanism 35 iselectrically connected to the battery cover 34 with the PTC device 36 inbetween. In the safety valve mechanism 35, when the internal pressurebecomes a certain level or more by internal short circuit, externalheating or the like, a disk plate 35A flips to cut the electricconnection between the battery cover 34 and the spirally wound electrodebody 40. When temperature rises, the PTC device 36 increases theresistance and thereby limits a current to prevent abnormal heatgeneration resulting from a large current. The gasket 37 is made of, forexample, an insulating material and its surface is coated with asphalt.

A center pin 44 may be inserted in the center of the spirally woundelectrode body 40. In the spirally wound electrode body 40, a cathodelead 45 made of aluminum or the like is connected to the cathode 41, andan anode lead 46 made of nickel or the like is connected to the anode42. The cathode lead 45 is electrically connected to the battery cover34 by being welded to the safety valve mechanism 35. The anode lead 46is welded and thereby electrically connected to the battery can 31.

The cathode 41 has a structure in which, for example, a cathode activematerial layer 41B is provided on the both faces of a strip-shapedcathode current collector 41A. The anode 42 has a structure similar tothat of the foregoing anode, for example, a structure in which an anodeactive material layer 42B and a coat 42C are provided on the both facesof a strip-shaped anode current collector 42A. The structures of thecathode current collector 41A, the cathode active material layer 41B,the anode current collector 42A, the anode active material layer 42B,the coat 42C, and the separator 43 and the composition of theelectrolytic solution are respectively similar to the structures of thecathode current collector 21A, the cathode active material layer 21B,the anode current collector 22A, the anode active material layer 22B,the coat 22C, and the separator 23 and the composition of theelectrolytic solution in the foregoing first battery.

The secondary battery is manufactured, for example, as follows.

First, for example, the cathode 41 is formed by forming the cathodeactive material layer 41B on the both faces of the cathode currentcollector 41A and the anode 42 is formed by forming the anode activematerial layer 42B and the coat 42C on the both faces of the anodecurrent collector 42A by respective procedures similar to the proceduresof forming the cathode 21 and the anode 22 in the foregoing firstbattery. Subsequently, the cathode lead 45 is attached to the cathode41, and the anode lead 46 is attached to the anode 42. Subsequently, thecathode 41 and the anode 42 are spirally wound with the separator 43 inbetween, and thereby the spirally wound electrode body 40 is formed. Theend of the cathode lead 45 is connected to the safety valve mechanism35, and the end of the anode lead 46 is connected to the battery can 31.After that, the spirally wound electrode body 40 is sandwiched betweenthe pair of insulating plates 32 and 33, and contained in the batterycan 31. Subsequently, the electrolytic solution is injected into thebattery can 31 and impregnated in the separator 43. Finally, at the openend of the battery can 31, the battery cover 34, the safety valvemechanism 35, and the PTC device 36 are fixed by being caulked with thegasket 37. The secondary battery shown in FIG. 7 and FIG. 8 is therebycompleted.

In the secondary battery, when charged, for example, lithium ions areextracted from the cathode 41 and inserted in the anode 42 through theelectrolytic solution impregnated in the separator 43. Meanwhile, whendischarged, for example, lithium ions are extracted from the anode 42,and inserted in the cathode 41 through the electrolytic solutionimpregnated in the separator 43.

According to the cylindrical secondary battery, the anode 42 has thestructure similar to that of the foregoing anode. Thus, the cyclecharacteristics can be improved. Effects of the secondary battery otherthan the foregoing effects are similar to those of the first battery.

Third Battery

FIG. 9 shows an exploded perspective structure of a third battery. FIG.10 shows a cross section taken along line X-X shown in FIG. 9. Thebattery is, as described above, a lithium ion secondary battery in whichthe capacity of an anode 54 is expressed based on insertion andextraction of lithium as an electrode reactant. In the battery, aspirally wound electrode body 50 on which a cathode lead 51 and an anodelead 52 are attached is contained in a film package member 60. Thebattery structure including the package member 60 is a so-calledlaminated film structure.

The cathode lead 51 and the anode lead 52 are respectively directed frominside to outside of the package member 60 in the same direction, forexample. The cathode lead 51 is made of, for example, a metal materialsuch as aluminum, and the anode lead 52 is made of, for example, a metalmaterial such as copper, nickel, and stainless. The metal materials arein the shape of a thin plate or mesh.

The package member 60 is made of an aluminum laminated film in which,for example, a nylon film, an aluminum foil, and a polyethylene film arebonded together in this order. The package member 60 has, for example, astructure in which the respective outer edges of 2 pieces of rectanglealuminum laminated films are bonded to each other by fusion bonding oran adhesive so that the polyethylene film and the spirally woundelectrode body 50 are opposed to each other.

An adhesive film 61 to protect from entering of outside air is insertedbetween the package member 60 and the cathode lead 51, the anode lead52. The adhesive film 61 is made of a material having contactcharacteristics to the cathode lead 51 and the anode lead 52. Examplesof such a material include, for example, a polyolefin resin such aspolyethylene, polypropylene, modified polyethylene, and modifiedpolypropylene.

The package member 60 may be made of a laminated film having otherlamination structure, a polymer film such as polypropylene, or a metalfilm, instead of the foregoing aluminum laminated film.

FIG. 11 shows an enlarged part of the spirally wound electrode body 50shown in FIG. 10. In the spirally wound electrode body 50, a cathode 53and an anode 54 are layered with a separator 55 and an electrolyte 56 inbetween and then spirally wound. The outermost periphery thereof isprotected by a protective tape 57.

The cathode 53 has a structure in which, for example, a cathode activematerial layer 53B is provided on the both faces of a cathode currentcollector 53A having a pair of opposed faces. The anode 54 has astructure similar to that of the foregoing anode, for example, has astructure in which an anode active material layer 54B and a coat 54C areprovided on the both faces of a strip-shaped anode current collector54A. The structures of the cathode current collector 53A, the cathodeactive material layer 53B, the anode current collector 54A, the anodeactive material layer 54B, the coat 54C, and the separator 55 arerespectively similar to those of the cathode current collector 21A, thecathode active material layer 21B, the anode current collector 22A, theanode active material layer 22B, the coat 22C, and the separator 23 ofthe foregoing first battery.

The electrolyte 56 is a so-called gel electrolyte, containing anelectrolytic solution and a polymer compound that holds the electrolyticsolution. The gel electrolyte is preferable, since thereby high ionconductivity (for example, 1 mS/cm or more at room temperature) isobtained and liquid leakage can be prevented.

As the polymer compound, for example, polyacrylonitrile, polyvinylidenefluoride, a copolymer of polyvinylidene fluoride and polyhexafluoropropylene, polytetrafluoro ethylene, polyhexafluoro propylene,polyethylene oxide, polypropylene oxide, polyphosphazene, polysiloxane,polyvinyl acetate, polyvinyl alcohol, polymethylmethacrylate,polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber,nitrile-butadiene rubber, polystyrene, polycarbonate or the like iscited. One of these polymer compounds may be used singly, or a pluralitythereof may be used by mixture. Specially, as a polymer compound,polyacrylonitrile, polyvinylidene fluoride, polyhexafluoro propylene,polyethylene oxide or the like is preferably used, since such a compoundis electrochemically stable.

The composition of the electrolytic solution is similar to thecomposition of the electrolytic solution in the first battery. However,in this case, the solvent means a wide concept including not only theliquid solvent but also a solvent having ion conductivity capable ofdissociating the electrolyte salt. Therefore, when the polymer compoundhaving ion conductivity is used, the polymer compound is also includedin the solvent.

Instead of the gel electrolyte 56 in which the electrolytic solution isheld by the polymer compound, the electrolytic solution may be directlyused. In this case, the electrolytic solution is impregnated in theseparator 55.

The secondary battery including the gel electrolyte 56 is manufactured,for example, by the following three manufacturing methods.

In the first manufacturing method, first, the cathode 53 is formed byforming the cathode active material layer 53B on the both faces of thecathode current collector 53A, and the anode 34 is formed by forming theanode active material layer 54B and the coat 54C on the both faces ofthe anode current collector 54A by a procedure similar to that of themethod of manufacturing the first battery. Subsequently, a precursorsolution containing an electrolytic solution, a polymer compound, and asolvent is prepared. After the cathode 53 and the anode 54 are coatedwith the precursor solution, the solvent is volatilized to form the gelelectrolyte 56. Subsequently, the cathode lead 51 is welded to thecathode current collector 53A, and the anode lead 52 is welded to theanode current collector 54A. Subsequently, the cathode 53 and the anode54 provided with the electrolyte 56 are layered with the separator 55 inbetween to obtain a laminated body. After that, the laminated body isspirally wound in the longitudinal direction, the protective tape 57 isadhered to the outermost periphery thereof to form the spirally woundelectrode body 50. Finally, for example, after the spirally woundelectrode body 50 is sandwiched between 2 pieces of the film packagemembers 60, outer edges of the package members 60 are contacted bythermal fusion bonding or the like to enclose the spirally woundelectrode body 50. At this time, the adhesive films 61 are insertedbetween the cathode lead 51, the anode lead 52 and the package member60. Thereby, the secondary battery shown in FIG. 9 to FIG. 11 iscompleted.

In the second manufacturing method, first, the cathode lead 51 is weldedto the cathode 53, and the anode lead 52 is welded to the anode 54.After that, the cathode 53 and the anode 54 are layered with theseparator 55 in between and spirally wound. The protective tape 57 isadhered to the outermost periphery thereof, and thereby a spirally woundbody as a precursor of the spirally wound electrode body 50 is formed.Subsequently, after the spirally wound body is sandwiched between 2pieces of the film package members 60, the outermost peripheries exceptfor one side are bonded by thermal fusion bonding or the like to obtaina pouched state, and the spirally wound body is contained in thepouch-like package member 60. Subsequently, a composition of matter forelectrolyte containing an electrolytic solution, a monomer as a rawmaterial for the polymer compound, a polymerization initiator, and ifnecessary other material such as a polymerization inhibitor is prepared,which is injected into the pouch-like package member 60. After that, theopening of the package member 60 is hermetically sealed by thermalfusion bonding or the like. Finally, the monomer is thermallypolymerized to obtain a polymer compound. Thereby, the gel electrolyte56 is formed. Accordingly, the secondary battery is completed.

In the third manufacturing method, the spirally wound body is formed andcontained in the pouch-like package member 60 in the same manner as thatof the foregoing second manufacturing method, except that the separator55 with the both faces coated with a polymer compound is used firstly.As the polymer compound with which the separator 55 is coated, forexample, a polymer containing vinylidene fluoride as a component, thatis, a homopolymer, a copolymer, a multicomponent copolymer and the likeare cited. Specifically, polyvinylidene fluoride, a binary copolymercontaining vinylidene fluoride and hexafluoro propylene as a component,a ternary copolymer containing vinylidene fluoride, hexafluoropropylene, and chlorotrifluoroethylene as a component and the like arecited. As a polymer compound, in addition to the foregoing polymercontaining vinylidene fluoride as a component, another one or morepolymer compounds may be contained. Subsequently, an electrolyticsolution is injected into the package member 60. After that, the openingof the package member 60 is sealed by thermal fusion bonding or thelike. Finally, the resultant is heated while a weight is applied to thepackage member 60, and the separator 55 is contacted to the cathode 53and the anode 54 with the polymer compound in between. Thereby, theelectrolytic solution is impregnated into the polymer compound, and thepolymer compound is gelated to form the electrolyte 56. Accordingly, thesecondary battery is completed.

In the third manufacturing method, the swollenness of the secondarybattery is prevented compared to the first manufacturing method.Further, in the third manufacturing method, the monomer, the solvent andthe like as a raw material of the polymer compound are hardly left inthe electrolyte 56 compared to the second manufacturing method, and theformation step of the polymer compound is favorably controlled. Thus,sufficient contact characteristics are obtained between the cathode53/the anode 54/the separator 55 and the electrolyte 56.

According to the laminated film secondary battery, the anode 54 has thestructure similar to that of the foregoing anode. Thus, the cyclecharacteristics can be improved. Effects of the secondary battery otherthan the foregoing effects are similar to those of the first battery.

EXAMPLES

Examples of the invention will be described in detail.

Example 1-1

The laminated film secondary battery shown in FIG. 9 to FIG. 11 wasmanufactured by the following procedure. The secondary battery wasmanufactured as a lithium ion secondary battery in which the capacity ofthe anode 54 was expressed based on insertion and extraction of lithium.

First, the cathode 53 was formed. First, lithium carbonate (Li₂CO₃) andcobalt carbonate (CoCO₃) were mixed at a molar ratio of 0.5:1. Afterthat, the mixture was fired in the air at 900 deg C. for 5 hours.Thereby, lithium cobalt complex oxide (LiCoO₂) was obtained.Subsequently, 91 parts by mass of the lithium cobalt complex oxide as acathode active material, 6 parts by mass of graphite as an electricalconductor, and 3 parts by mass of polyvinylidene fluoride as a binderwere mixed to obtain a cathode mixture. After that, the cathode mixturewas dispersed in N-methyl-2-pyrrolidone to obtain paste cathode mixtureslurry. Finally, the both faces of the cathode current collector 53Amade of a strip-shaped aluminum foil (thickness: 12 μm thick) wereuniformly coated with the cathode mixture slurry, which was dried. Afterthat, the resultant was compression-molded by a roll pressing machine toform the cathode active material layer 53B.

Next, the anode 54 was formed. First, the anode current collector 54Amade of an electrolytic copper foil (thickness: 18 μm, ten point heightroughness profile Rz: 3.5 μm) was prepared. Subsequently, as an anodeactive material, silicon was deposited on the both faces of the anodecurrent collector 54A by electron beam evaporation method using adeflective electron beam evaporation source, and thereby the anodeactive material layer 54B containing a plurality of particulate anodeactive materials was formed. When the anode active material layer 54Bwas formed, silicon with the purity of 99% was used as the evaporationsource, the deposition rate was 10 nm/sec, and the anode active materialwas formed to have a single layer structure (thickness: 7.5 μm).Further, oxygen gas and if necessary moisture vapor were continuouslyintroduced into the chamber so that the oxygen content in the anodeactive material was 3 atomic %. Finally, the fluorine resin having thestructure shown in Chemical formula 1 was dispersed in a Galden solventto prepare a 2 wt % solution. The anode current collector 54A on whichthe anode active material layer 54B was formed was dipped into thesolution over 30 sec, taken out, and dried to form the coat 54C. Whenthe coat 54C was formed, as the fluorine resin having the structureshown in Chemical formula 3 and Chemical formula 4 (X=Chemical formula1), a fluorine resin in which the terminals (R1 and R2) have thestructure shown in Chemical formula 18(1) was used.

Next, after ethylene carbonate (EC) and diethyl carbonate (DEC) weremixed as a solvent, lithium hexafluorophosphate (LiPF₆) was dissolvedtherein as an electrolyte salt to prepare an electrolytic solution. Thecomposition of the solvent (EC:DEC) was 50:50 at a weight ratio. Theconcentration of the electrolyte salt in the electrolytic solution was 1mol/kg.

Next, the secondary battery was assembled by using the cathode 53, theanode 54, and the electrolytic solution. First, the cathode lead 51 madeof aluminum was welded to one end of the cathode current collector 53A,and the anode lead 52 made of nickel was welded to one end of the anodecurrent collector 54A. Subsequently, the cathode 53, the 3-layerseparator 55 (thickness: 23 μm) in which a film made of a porouspolyethylene as a main component was sandwiched between films made ofporous polypropylene as a main component, the anode 54, and theforegoing polymer separator 55 were layered in this order. The resultantlaminated body was spirally wound in the longitudinal direction, the endportion of the spirally wound body was fixed by the protective tape 57made of an adhesive tape, and thereby a spirally wound body as aprecursor of the spirally wound electrode body 50 was formed.Subsequently, the spirally wound body was sandwiched between the packagemembers 60 made of a 3-layer laminated film (total thickness: 100 μm) inwhich a nylon film (thickness: 30 μm), an aluminum foil (thickness: 40μm), and a non-stretch polypropylene (thickness 30 μm) were layered fromthe outside. After that, outer edges other than an edge of one side ofthe package members were thermally fusion-bonded to each other. Thereby,the spirally wound body was contained in the package members 60 in apouched state. Subsequently, an electrolytic solution was injectedthrough the opening of the package member 60, the electrolytic solutionwas impregnated in the separator 55, and thereby the spirally woundelectrode body 50 was formed. Finally, the opening of the package member60 was sealed by thermal fusion bonding in the vacuum atmosphere, andthereby the laminated film secondary battery was completed.

Examples 1-2 to 1-4

A procedure was performed in the same manner as that of Example 1-1,except that a fluorine resin in which R1 and R2 had the structure shownin Chemical formula 18(2) (Example 1-2), a fluorine resin in which R1and R2 had the structure shown in Chemical formula 18(3) (Example 1-3),or a fluorine resin in which R1 and R2 had the structure shown inChemical formula 18(4) (Example 1-4) were used instead of the fluorineresin in which R1 and R2 had the structure shown in Chemical formula18(1).

Examples 1-5 to 1-11

A procedure was performed in the same manner as that of Example 1-1,except that a fluorine resin in which R1 and R2 had the structure shownin Chemical formula 19(1) (Example 1-5), a fluorine resin in which R1and R2 had the structure shown in Chemical formula 19(2) (Example 1-6),a fluorine resin in which R1 and R2 had the structure shown in Chemicalformula 19(3) (Example 1-7), a fluorine resin in which R1 and R2 had thestructure shown in Chemical formula 19(4) (Example 1-8), a fluorineresin in which R1 and R2 had the structure shown in Chemical formula19(5) (Example 1-9), a fluorine resin in which R1 and R2 had thestructure shown in Chemical formula 19(6) (Example 1-10), or a fluorineresin in which R1 or R2 had the structure shown in Chemical formula19(7) (Example 1-11) was used instead of the fluorine resin in which R1and R2 had the structure shown in Chemical formula 18(1).

Examples 1-12 to 1-16

A procedure was performed in the same manner as that of Example 1-1,except that a fluorine resin in which R1 and R2 had the structure shownin Chemical formula 20(1) (Example 1-12), a fluorine resin in which R1and R2 had the structure shown in Chemical formula 20(2) (Example 1-13),a fluorine resin in which R1 and R2 had the structure shown in Chemicalformula 20(3) (Example 1-14), a fluorine resin in which R1 and R2 hadthe structure shown in Chemical formula 20(4) (Example 1-15), or afluorine resin in which R1 and R2 had the structure shown in Chemicalformula 20(5) (Example 1-16) was used instead of the fluorine resin inwhich R1 and R2 had the structure shown in Chemical formula 18(1).

Example 1-17

A procedure was performed in the same manner as that of Example 1-1,except that a fluorine resin in which R1 and R2 were a trifluoromethylgroup was used instead of the fluorine resin in which R1 and R2 had thestructure shown in Chemical formula 18(1).

Comparative Example 1

A procedure was performed in the same manner as that of Example 1-1,except that the coat 54C was not formed.

When the cycle characteristics of the secondary batteries of Examples1-1 to 1-17 and Comparative example 1 were examined, the results shownin Table 1 were obtained.

In examining the cycle characteristics, first, to stabilize the batterystate, charge and discharge were performed one cycle at 23 deg C. Afterthat, charge and discharge were performed in the same atmosphere tomeasure the discharge capacity at the second cycle. Subsequently, thesecondary battery was charged and discharged 99 cycles in the sameatmosphere, and thereby the discharge capacity at the 101st cycle wasmeasured. After that, the discharge capacity retention ratio(%)=(discharge capacity at the 101st cycle/discharge capacity at thesecond cycle)×100 was calculated. At the time of charge, charge wasperformed at the constant current density of 3 mA/cm² until the batteryvoltage reached 4.2 V, and then charge was continuously performed at theconstant voltage of 4.2 V until the current density reached 0.3 mA/cm².In discharge, discharge was performed at the constant current density of3 mA/cm² until the battery voltage reached 2.5 V.

The procedure and the conditions for examining the cycle characteristicswere similarly applied to the following series of examples andcomparative examples.

TABLE 1 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz: 3.5 μm Oxygencontent in the anode active material: 3 atomic % Anode active materiallayer Discharge Number of anode capacity active material Coat retentionlayers (layer) X R1 and R2 ratio (%) Example 1-1 1 Chemical formula 1Chemical formula 18(1) 88 Example 1-2 Chemical formula 18(2) 87 Example1-3 Chemical formula 18(3) 87 Example 1-4 Chemical formula 18(4) 86Example 1-5 Chemical formula 19(1) 85 Example 1-6 Chemical formula 19(2)85 Example 1-7 Chemical formula 19(3) 84 Example 1-8 Chemical formula19(4) 84 Example 1-9 Chemical formula 19(5) 84 Example 1-10 Chemicalformula 19(6) 83 Example 1-11 Chemical formula 19(7) 83 Example 1-12Chemical formula 20(1) 82 Example 1-13 Chemical formula 20(2) 82 Example1-14 Chemical formula 20(3) 82 Example 1-15 Chemical formula 20(4) 81Example 1-16 Chemical formula 20(5) 81 Example 1-17 Trifluoro methylgroup 75 Comparative 1 — — 45 example 1

As shown in Table 1, when the fluorine resin having the structure shownin Chemical formula 1 was used and the anode active material was formedinto the single-layer structure, in Examples 1-1 to 1-17 in which thecoat 54C containing the fluorine resin was formed, the dischargecapacity retention ratio was significantly higher than that ofComparative example 1 in which the coat 54C was not formed. In thiscase, in Examples 1-1 to 1-16 in which the terminals had the structureshown in Chemical formula 18(1) or the like, the discharge capacityretention ratio was significantly higher than that of Example 1-17 inwhich the terminals were the trifluoromethyl group. The dischargecapacity retention ratio of Examples 1-1 to 1-16 tended to exceed 80%.Accordingly, it was confirmed that in the secondary battery of theinvention, the cycle characteristics were improved when the coat 54Ccontaining the fluorine resin having the structure shown in Chemicalformula 1 was provided on the anode active material layer 54B. In thiscase, it was also confirmed that when the fluorine resin had thestructure shown in Chemical formula 3 or Chemical formula 4, thecharacteristics were further improved.

Examples 2-1 to 2-6

A procedure was performed in the same manner as that of Examples 1-1 and1-5 to 1-9, except that the anode active material was formed into6-layer structure. Silicon was sequentially deposited while the anodecurrent collector 54A was reciprocated to an evaporation source at thedeposition rate of 100 nm/sec.

Examples 3-1 to 3-6

A procedure was performed in the same manner as that of Examples 1-1 and1-5 to 1-9, except that the anode active material was formed into12-layer structure by a step similar to that of Examples 2-1 to 2-6.

Examples 4-1 to 4-6

A procedure was performed in the same manner as that of Examples 1-1 and1-5 to 1-9, except that the anode active material was formed into24-layer structure by a step similar to that of Examples 2-1 to 2-6.

Comparative Example 2

A procedure was performed in the same manner as that of Comparativeexample 1, except that the anode active material was formed into 6-layerstructure as in Examples 2-1 to 2-6.

Comparative Example 3

A procedure was performed in the same manner as that of Comparativeexample 1, except that the anode active material was formed into12-layer structure as in Examples 3-1 to 3-6.

Comparative Example 4

A procedure was performed in the same manner as that of Comparativeexample 1, except that the anode active material was formed into24-layer structure as in Examples 4-1 to 4-6.

When the cycle characteristics of the secondary batteries of Examples2-1 to 2-6, 3-1 to 3-6, and 4-1 to 4-6 and Comparative examples 2 to 4were examined, the results shown in Table 2 to Table 4 were obtained.

TABLE 2 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz: 3.5 μm Oxygencontent in the anode active material: 3 atomic % Anode active materiallayer Discharge Number of anode capacity active material Coat retentionlayers (layer) X R1 and R2 ratio (%) Example 2-1 6 Chemical formula 1Chemical formula 18(1) 89 Example 2-2 Chemical formula 19(1) 87 Example2-3 Chemical formula 19(2) 86 Example 2-4 Chemical formula 19(3) 86Example 2-5 Chemical formula 19(4) 85 Example 2-6 Chemical formula 19(5)85 Comparative 6 — — 46 example 2

TABLE 3 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz: 3.5 μm Oxygencontent in the anode active material: 3 atomic % Anode active materiallayer Discharge Number of anode capacity active material Coat retentionlayers (layer) X R1 and R2 ratio (%) Example 3-1 12 Chemical formula 1Chemical formula 18(1) 90 Example 3-2 Chemical formula 19(1) 89 Example3-3 Chemical formula 19(2) 88 Example 3-4 Chemical formula 19(3) 87Example 3-5 Chemical formula 19(4) 87 Example 3-6 Chemical formula 19(5)86 Comparative 12 — — 47 example 3

TABLE 4 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz: 3.5 μm Oxygencontent in the anode active material: 3 atomic % Anode active materiallayer Discharge Number of anode capacity active material Coat retentionlayers (layer) X R1 and R2 ratio (%) Example 4-1 24 Chemical formula 1Chemical formula 18(1) 90.5 Example 4-2 Chemical formula 19(1) 90Example 4-3 Chemical formula 19(2) 89 Example 4-4 Chemical formula 19(3)89 Example 4-5 Chemical formula 19(4) 88 Example 4-6 Chemical formula19(5) 88 Comparative 24 — — 48 example 4

As shown in Table 2 to Table 4, when the anode active material wasformed into the multilayer structure, results similar to the results ofTable 1 were obtained as well. That is, in Examples 2-1 to 2-6, 3-1 to3-6, and 4-1 to 4-6 in which the coat 54C containing the fluorine resinwas formed, the discharge capacity retention ratio was significantlyhigher than that of Comparative examples 2 to 4 in which the coat 54Cwas not formed. In this case, when comparison was made among Examples1-1, 2-1, 3-1, and 4-1 that had the structure similar to each otherexcept for the number of anode active material layers, there was atendency that the discharge capacity retention ratio in the case thatthe anode active material had the multilayer structure was higher thanthat in the case that the anode active material had the single layerstructure, and the discharge capacity retention ratio became higher asthe number of layers was increased. Accordingly, it was confirmed thatin the secondary battery of the invention, when the anode activematerial was formed into the multilayer structure, the cyclecharacteristics were improved as well. It was also confirmed that whenthe number of anode active material layers was increased, thecharacteristics were further improved.

Examples 5-1 to 5-7

A procedure was performed in the same manner as that of Examples 1-1,1-5 to 1-9, and 1-17, except that the fluorine resin having thestructure shown in Chemical formula 2 (X=Chemical formula 2) was usedinstead of the structure shown in Chemical formula 1.

Comparative Example 5

A procedure was performed in the same manner as that of Comparativeexample 1, except that the fluorine resin having the structure shown inChemical formula 2 was used as in Examples 5-1 to 5-7.

When the cycle characteristics of the secondary batteries of Examples5-1 to 5-7 and Comparative example 5 were examined, the results shown inTable 5 were obtained.

TABLE 5 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz: 3.5 μm Oxygencontent in the anode active material: 3 atomic % Anode active materiallayer Discharge Number of anode capacity active material Coat retentionlayers (layer) X R1 and R2 ratio (%) Example 5-1 1 Chemical formula 2Chemical formula 18(1) 87 Example 5-2 Chemical formula 19(1) 85 Example5-3 Chemical formula 19(2) 84 Example 5-4 Chemical formula 19(3) 84Example 5-5 Chemical formula 19(4) 83 Example 5-6 Chemical formula 19(5)83 Example 5-7 Trifluoromethyl group 75 Comparative 1 — — 44 example 5

As shown in Table 5, when the fluorine resin having the structure shownin Chemical formula 2 was used, results similar to the results of Table1 could be obtained as well. That is, in Examples 5-1 to 5-7 in whichthe coat 54C containing the fluorine resin was formed, the dischargecapacity retention ratio was significantly higher than that ofComparative example 5 in which the coat 54C was not formed. In thiscase, when the terminal (R1 and R2) had the structure shown in Chemicalformula 18(1) or the like, the discharge capacity retention ratio wassignificantly higher than that of the case in which the terminal was thetrifluoromethyl group. The discharge capacity retention ratio of theformer tended to exceed 80%. Accordingly, it was confirmed that in thesecondary battery of the invention, the cycle characteristics wereimproved when the coat 54C containing the fluorine resin having thestructure shown in Chemical formula 2 was provided on the anode activematerial layer 54B. In this case, it was also confirmed that when thefluorine resin had the structure shown in Chemical formula 3 or Chemicalformula 4, the characteristics were further improved.

As a representative of the series of examples and comparative examplesdescribed above, when the surface of the anodes 54 for the secondarybatteries of Examples 1-1 and 1-5 were observed, the results shown inFIG. 12 and FIG. 13 were obtained. FIG. 12 and FIG. 13 are respectivelyan SEM photograph showing a cross sectional structure of the anode 54 ofExamples 1-1 and 1-5. When the surface of the anode 54 was observed, asecondary battery used for examining generation state of a fluoride ofthe electrode reactant was manufactured besides a secondary battery usedfor examining the cycle characteristics. The former secondary batterywas charged and discharged 30 cycles and then decomposed. Then, theanode 54 was taken out, and the surface thereof was observed by SEM.

As shown in FIG. 12 and FIG. 13, in both Example 1-1 and Example 1-5, aplurality of particulate anode active materials were observed, and afluoride (lithium fluoride) of lithium as the electrode reactant wasobserved on the surface thereof. In this case, in Example 1-1 (FIG. 12),the lithium fluoride was in a state of a coat divided into a pluralityof sections. Meanwhile, in Example 1-5 (FIG. 13), the lithium fluoridewas in a state of a plurality of particles. Such a difference of thelithium fluoride may result from the fluorine resin type (difference ofthe group existing at the terminal). Accordingly, it was confirmed thatin the secondary battery of the invention, when charge and dischargewere performed after the coat 54C containing the fluorine resin wasformed, the lithium fluoride in a state of a coat or in a state ofparticles were generated on the surface of the coat 54C.

Examples 6-1 to 6-4

A procedure was performed in the same manner as that of Examples 1-1,1-5, 1-6, and 1-8, except that the anode active material layer 54B wasformed by sintering method instead of electron beam evaporation method.The anode active material layer 54B was formed as follows. First, 90parts by mass of silicon powder as an anode active material (averageparticle diameter: 6 μm) and 10 parts by mass of polyvinylidene fluorideas a binder were mixed to obtain an anode mixture. After that, the anodemixture was dispersed in N-methyl-2-pyrrolidone to obtain paste anodemixture slurry. Subsequently, the both faces of the anode currentcollector 54A were uniformly coated with the anode mixture slurry, andthen such a resultant coat was compression-molded by a rolling pressmachine. Finally, the coat was heated at 220 deg C. for 12 hours in thevacuum atmosphere. The foregoing average particle diameter was aso-called median size. The same will be applied to the followingdescription.

Comparative Example 6

A procedure was performed in the same manner as that of Comparativeexample 1, except that the anode active material layer 54B was formed bysintering method as in Examples 6-1 to 6-4.

When the cycle characteristics of the secondary batteries of Examples6-1 to 6-4 and Comparative example 6 were examined, the results shown inTable 6 were obtained.

TABLE 6 Anode active material: silicon (sintering method) Ten pointsaverage height of roughness profile Rz: 3.5 μm Discharge capacity Coatretention X R1 and R2 ratio (%) Example 6-1 Chemical formula 1 Chemicalformula 18(1) 84 Example 6-2 Chemical formula 19(1) 84 Example 6-3Chemical formula 19(2) 83 Example 6-4 Chemical formula 19(4) 83Comparative — — 72 example 6

As shown in Table 6, when the anode active material layer 54B was formedby sintering method, results similar to the results of Table 1 could beobtained as well. That is, in Examples 6-1 to 6-4 in which the coat 54Ccontaining the fluorine resin was formed, the discharge capacityretention ratio was higher than that of Comparative example 6 in whichthe coat 54C was not formed. Accordingly, it was confirmed that in thesecondary battery of the invention, the cycle characteristics wereimproved as well when the anode active material layer 54B was formed bysintering method.

Examples 7-1 to 7-4

A procedure was performed in the same manner as that of Examples 1-1,1-5, 1-6, and 1-8, except that the anode active material layer 54B wasformed by using an alloy containing tin instead of silicon as an anodeactive material. The anode active material layer 54B was formed asfollows. First, powder tin-cobalt alloy was formed by gas atomizingmethod. (The atomicity ratio was Sn:Co=80:20.) After that, the resultanttin-cobalt alloy was pulverized and classified until the averageparticle diameter became 15 μm. Subsequently, 75 parts by mass of thetin-cobalt alloy powder as an anode active material, 20 parts by mass ofscale-like graphite as an electrical conductor, and 5 parts by mass ofcarboxymethyl cellulose as a thickener were mixed to obtain an anodemixture. After that, the anode mixture was dispersed in pure water toobtain anode mixture slurry. Finally, the both faces of the anodecurrent collector 54A were uniformly coated with the anode mixtureslurry, and then such a resultant coat was compression-molded by arolling press machine. The completed anode 54 was analyzed by augerelectron spectrometer (AES). As a result, it was confirmed that theanode current collector 54A and the anode active material layer 54B werealloyed in at least part of the interface in between.

Comparative Example 7

A procedure was performed in the same manner as that of Comparativeexample 1, except that the anode active material layer 54B was formed byusing a tin-cobalt alloy as an anode active material as in Examples 7-1to 7-4.

When the cycle characteristics of the secondary batteries of Examples7-1 to 7-4 and Comparative example 7 were examined, the results shown inTable 7 were obtained.

TABLE 7 Anode active material: tin-cobalt alloy (coating method) Tenpoints average height of roughness profile Rz: 3.5 μm Discharge capacityCoat retention X R1 and R2 ratio (%) Example 7-1 Chemical formula 1Chemical formula 18(1) 83 Example 7-2 Chemical formula 19(1) 82 Example7-3 Chemical formula 19(2) 81 Example 7-4 Chemical formula 19(4) 80Comparative — — 75 example 7

As shown in Table 7, when the anode active material layer 54B was formedby using the tin-cobalt alloy, results similar to the results of Table 1were obtained as well. That is, in Examples 7-1 to 7-4 in which the coat54C containing the fluorine resin was formed, the discharge capacityretention ratio was higher than that of Comparative example 7 in whichthe coat 54C was not formed. Accordingly, it was confirmed that in thesecondary battery of the invention, the cycle characteristics wereimproved as well when the alloy containing tin was used as an anodeactive material.

Examples 8-1 to 8-3

A procedure was performed in the same manner as that of Examples 1-1,1-5, and 1-6, except that the anode active material layer 54B was formedby using a carbon material instead of silicon as an anode activematerial. The anode active material layer 54B was formed as follows. 87parts by mass of mesophase carbon micro beads (MCMB: average particlediameter: 25 μm) and 3 parts by mass of graphite as an anode activematerial, and 10 parts by mass of polyvinylidene fluoride as a binderwere mixed to obtain a cathode mixture. After that, the anode mixturewas dispersed in N-methyl-2-pyrrolidone to obtain paste anode mixtureslurry. After that, the both faces of the anode current collector 54Awere uniformly coated with the anode mixture slurry, dried, and thensuch a resultant coat was compression-molded by a rolling press machine.

Comparative Example 8

A procedure was performed in the same manner as that of Comparativeexample 1, except that the anode active material layer 54B was formed byusing the carbon material as an anode active material as in Examples 8-1to 8-3.

When the cycle characteristics of the secondary batteries of Examples8-1 to 8-3 and Comparative example 8 were examined, the results shown inTable 8 were obtained.

TABLE 8 Anode active material: MCMB (coating method) Ten points averageheight of roughness profile Rz: 3.5 μm Discharge capacity Coat retentionX R1 and R2 ratio (%) Example 8-1 Chemical formula 1 Chemical formula18(1) 90 Example 8-2 Chemical formula 19(1) 90 Example 8-3 Chemicalformula 19(2) 90 Comparative — — 87 example 8

As shown in Table 8, when the anode active material layer 54B was formedby using the carbon material, results similar to the results of Table 1were obtained as well. That is, in Examples 8-1 to 8-3 in which the coat54C containing the fluorine resin was formed, the discharge capacityretention ratio was higher than that of Comparative example 7 in whichthe coat 54C was not formed. Accordingly, it was confirmed that in thesecondary battery of the invention, the cycle characteristics wereimproved as well when the carbon material was used as an anode activematerial.

Examples 9-1 to 9-6

A procedure was performed in the same manner as that of Example 4-1,except that the oxygen content in the anode active material was changedto 2 atomic % (Example 19-1), 10 atomic % (Example 9-2), 20 atomic %(Example 9-3), 30 atomic % (Example 9-4), 40 atomic % (Example 9-5), or45 atomic % (Example 9-6) instead of 3 atomic %.

When the cycle characteristics of the secondary batteries of Examples9-1 to 9-6 were examined, the results shown in Table 9 and FIG. 14 wereobtained.

TABLE 9 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz = 3.5 μm Anodeactive material layer Number of anode Discharge active material Oxygencapacity particle layers content Coat retention (layer) (atomic %) X R1and R2 ratio (%) Example 9-1 24 2 Chemical formula 1 Chemical formula18(1) 88.5 Example 4-1 3 90.5 Example 9-2 10 90.8 Example 9-3 20 90.8Example 9-4 30 90.9 Example 9-5 40 91 Example 9-6 45 91 Comparative 24 3— — 48 example 4

As shown in Table 9, in Examples 9-1 to 9-6 in which the oxygen contentin the anode active material was different, the discharge capacityretention ratio was significantly higher as in Example 4-1 than that ofComparative example 4. In this case, as shown in Table 9 and FIG. 14, asthe oxygen content was increased, the discharge capacity retention ratiotended to be increased and then became almost constant. If the oxygencontent was smaller than 3 atomic %, the discharge capacity retentionratio tended to be largely decreased. However, if the oxygen content waslarger than 40 atomic %, the battery capacity tended to be loweredthough the discharge capacity retention ratio tended to be increased.Accordingly, it was confirmed that in the secondary battery of theinvention, the cycle characteristics were improved as well when theoxygen content in the anode active material was changed. Further, it wasconfirmed that if the oxygen content was 3 atomic % or more, thecharacteristics were further improved, and if the oxygen content was 3atomic % or more and 40 atomic % or less, the battery capacity wassecured.

Examples 10-1 to 10-6

A procedure was performed in the same manner as that of Example 4-1,except that the anode active material containing both silicon and ametal element was deposited by using silicon with purity of 99% and themetal element with purity of 99.9% as evaporation sources. As the metalelement, iron (Example 10-1), cobalt (Example 10-2), nickel (Example10-3), chromium (Example 10-4), titanium (Example 10-5), or molybdenum(Example 10-6) was used. The evaporation amount of the metal element wasadjusted so that the metal element content in the anode active materialwas 5 atomic %.

When the cycle characteristics of the secondary batteries of Examples10-1 to 10-6 were examined, the results shown in Table 10 were obtained.

TABLE 10 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz = 3.5 μmOxygen content in the anode active material: 3 atomic % Anode activematerial layer Number of anode Discharge active material capacityparticle layers Metal Coat retention (layer) element X R1 and R2 ratio(%) Example 4-1 24 — Chemical formula 1 Chemical formula 18(1) 90.5Example 10-1 Fe 91.1 Example 10-2 Co 92.1 Example 10-3 Ni 91 Example10-4 Cr 91.1 Example 10-5 Ti 91.2 Example 10-6 Mo 91.5

As shown in Table 10, in Examples 10-1 to 10-6 in which the anode activematerial contained the metal element together with silicon, thedischarge capacity retention ratio was higher than that of Example 4-1in which the anode active material did not contain the metal element.Accordingly, it was confirmed that in the secondary battery of theinvention, the cycle characteristics were further improved when theanode active material contained the metal element.

Examples 11-1 to 11-3

A procedure was performed in the same manner as that of Example 4-1,except that the anode active material was deposited so that the firstoxygen-containing region and the second oxygen-containing region havinga higher oxygen content than that of the first oxygen-containing regionwere alternately layered by depositing silicon while intermittentlyintroducing oxygen gas or the like into a chamber, instead of making theanode active material contain oxygen by depositing silicon whilecontinuously introducing oxygen gas or the like into a chamber. Theoxygen content in the second oxygen-containing region was 3 atomic %,and the number thereof was 6 (Example 11-1), 12 (Example 11-2), or 24(Example 11-3).

When the cycle characteristics of the secondary batteries of Examples11-1 to 11-3 were examined, the results shown in Table 11 and FIG. 15were obtained.

TABLE 11 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz = 3.5 μmOxygen content in the anode active material: 3 atomic % Anode activematerial layer Number of anode Number of Discharge active materialsecond oxygen- capacity particle layers containing Coat retention(layer) regions (pcs) X R1 and R2 ratio (%) Example 4-1 24 — Chemicalformula 1 Chemical formula 18(1) 90.5 Example 11-1 6 90.8 Example 11-212 91.2 Example 11-3 24 91.4

As shown in Table 11 and FIG. 15, in Examples 11-1 to 11-3 in which theanode active material had the first and the second oxygen-containingregions, the discharge capacity retention ratio was higher than that ofExample 4-1 in which the anode active material did not contain the firstand the second oxygen-containing regions. In this case, as the number ofthe second oxygen-containing regions was increased, the dischargecapacity retention ratio tended to be higher. Accordingly, it wasconfirmed that in the secondary battery of the invention, the cyclecharacteristics were improved when the anode active material had thefirst and the second oxygen-containing regions. Further, it wasconfirmed that as the number of the second oxygen-containing regions wasincreased, the characteristics were further improved.

Example 12-1

A procedure was performed in the same manner as that of Example 1-1,except that the anode active material layer 54B (thickness: 6.2 μm) wasformed by RF magnetron sputtering method instead of electron beamevaporation method. At that time, silicon with purity of 99.99% was usedas a target, and the deposition rate was 0.5 nm/sec.

Example 12-2

A procedure was performed in the same manner as that of Example 1-1,except that the anode active material layer 54B (thickness: 6.3 μm) wasformed by CVD method instead of electron beam evaporation method. Atthat time, silane and argon were used respectively as a raw material andexcitation gas, the deposition rate and the substrate temperature wererespectively 1.5 nm/sec and 200 deg C.

When the cycle characteristics of the secondary batteries of Examples12-1 and 12-2 were examined, the results shown in Table 12 wereobtained.

TABLE 12 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz = 3.5 μmOxygen content in the anode active material = 3 atomic % Anode activematerial layer Number of anode Discharge active material capacityparticle layers Coat retention (layer) Forming method X R1 and R2 ratio(%) Example 1-1 1 Electron beam Chemical formula 1 Chemical formula18(1) 88 evaporation method Example 12-1 Sputtering 85 method Example12-2 CVD method 86 Comparative 1 Electron beam — — 45 example 1evaporation method

As shown in Table 12, in Examples 12-1 and 12-2 in which the method offorming the anode active material layer 54B was different, the dischargecapacity retention ratio was higher as in Example 1-1 than that ofComparative example 1. In this case, the discharge capacity retentionratio tended to be increased in the case of using electron beamevaporation method than in the case of using sputtering method and inthe case of using CVD method. Accordingly, it was confirmed that in thesecondary battery of the invention, the cycle characteristics wereimproved as well when the method of forming the anode active materiallayer 54B was changed. Further, it was confirmed that when evaporationmethod was used, the characteristics were further improved.

Examples 13-1 to 13-7

A procedure was performed in the same manner as that of Example 4-1,except that the ten points average height of roughness profile Rz of thesurface of the anode current collector 54A was changed to 1 μm (Example3-1), 1.5 μm (Example 13-2), 2.5 μm (Example 13-3), 4.5 μm (Example13-4), 5.5 μm (Example 13-5), 6.5 μm (Example 13-6), or 7 μm (Example13-7) instead of 3.5 μm.

When the cycle characteristics of the secondary batteries of Examples13-1 to 13-7 were examined, the results shown in Table 13 and FIG. 16were obtained.

TABLE 13 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz = 3.5 μmOxygen content in the anode active material = 3 atomic % Anode currentAnode active collector material layer Ten points Number of Dischargeaverage height anode active capacity of roughness material particle Coatretention profile Rz (μm) layers (layer) X R1 and R2 ratio (%) Example13-1 1 24 Chemical formula 1 Chemical formula 18(1) 80.2 Example 13-21.5 85.5 Example 13-3 2.5 87.3 Example 4-1 3.5 90.5 Example 13-4 4.590.6 Example 13-5 5.5 90.5 Example 13-6 6.5 90.2 Example 13-7 7 81.3Comparative 3.5 24 — — 48 example 4

As shown in Table 13, in Examples 13-1 to 13-7 in which the ten pointsaverage height of roughness profile Rz was different, the dischargecapacity retention ratio was largely higher as in Example 4-1 than thatof Comparative example 4. In this case, as shown in Table 13 and FIG.16, as the ten points average height of roughness profile Rz wasincreased, the discharge capacity retention ratio tended to be increasedand then decreased, and if the ten points average height of roughnessprofile Rz was smaller than 1.5 μm or larger than 6.5 μm, the dischargecapacity retention ratio tended to be extremely lowered. Accordingly, itwas confirmed that in the secondary battery of the invention, the cyclecharacteristics were improved as well if the ten points average heightof roughness profile Rz of the surface of the anode current collector54A was changed. Further, it was confirmed that if the ten pointsaverage height of roughness profile Rz was 1.5 μm or more and 6.5 μm orless, the characteristics were further improved.

Example 14-1

A procedure was performed in the same manner as that of Example 4-1,except that the square secondary battery shown in FIG. 4 to FIG. 6 wasmanufactured by the following procedure instead of the laminated filmsecondary battery.

First, the cathode 21 and the anode 22 were formed. After that, thecathode lead 24 made of aluminum was welded to the cathode currentcollector 21A and the anode lead 25 made of nickel was welded to theanode current collector 22A. Subsequently, the cathode 21, the separator23, and the anode 22 were layered in this order, and spirally wound inthe longitudinal direction, and then formed in the flat shape. Thereby,the battery element 20 was formed. Subsequently, the battery element 20was contained in the battery can 11 made of aluminum. After that, theinsulating plate 12 was arranged on the battery element 20.Subsequently, the cathode lead 24 and the anode lead 25 wererespectively welded to the cathode pin 15 and the battery can 11. Afterthat, the battery cover 13 was fixed to the open end of the battery can11 by laser welding. Finally, the electrolytic solution was injectedinto the battery can 11 through the injection hole 19. After that, theinjection hole 19 was sealed by the sealing member 19A, and thereby thesquare battery was completed.

Example 14-2

A procedure was performed in the same manner as that of Example 14-1,except that the battery can 11 made of iron was used instead of thebattery can 11 made of aluminum.

When the cycle characteristics of the secondary batteries of Examples14-1 and 14-2 were examined, the results shown in Table 14 wereobtained.

TABLE 14 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz = 3.5 μmOxygen content in the anode active material = 3 atomic % Anode activematerial layer Number of anode Discharge active material capacityBattery particle layers Coat retention structure (layer) X R1 and R2ratio (%) Example 4-1 Laminated 24 Chemical formula 1 Chemical formula18(1) 90.5 film Example 14-1 Square 91.2 (aluminum) Example 14-2 Square92.3 (iron) Comparative Laminated 24 — — 48 example 4 film

As shown in Table 14, in Examples 14-1 and 14-2 in which the batterystructure was different, the discharge capacity retention ratio waslargely higher as in Example 4-1 than that of Comparative example 4 aswell. In this case, the discharge capacity retention ratio of Examples14-1 and 14-2 tended to be higher than that of Example 4-1, and thedischarge capacity retention ratio in the case that the battery can 11was made of iron was higher than that in the case that the battery can11 was made of aluminum. Accordingly, it was confirmed that in thesecondary battery of the invention, the cycle characteristics wereimproved as well when the battery structure was changed. Further, it wasconfirmed that in the case that the battery structure was the squaretype, the cycle characteristics were further improved than that in thecase that the battery structure was the laminated film type, and thecycle characteristics were further improved in the case that the batterycan 11 made of iron was used. Though no specific examples for acylindrical secondary battery in which the package member is made of ametal material have been herein given, it is evident that similareffects are obtained in such a cylindrical secondary battery since thecycle characteristics and the swollenness characteristics were improvedin the square secondary battery including the package member made of themetal material than in the laminated film secondary battery.

Example 15-1

A procedure was performed in the same manner as that of Example 4-1,except that 4-fluoro-1,3-dioxolane-2-one (FEC) as a cyclic estercarbonate having halogen shown in Chemical formula 22 was used insteadof EC as a solvent.

Example 15-2

A procedure was performed in the same manner as that of Example 15-1,except that as an electrolyte salt, lithium tetrafluoroborate (LiBF₄)was added and sulfobenzoic acid anhydride (SBAH) was added as an acidanhydride. While the concentration of the lithium hexafluoroborate inthe electrolytic solution was kept 1 mol/kg, the concentration oftetrafluoroborate in the electrolytic solution was set to 0.05 mol/kg.Further, the content of the SBAH in the solvent was 1 wt %. “Wt %”herein means a unit where the entire solvent was 100 wt %. The same willbe applied to the following descriptions.

Example 15-3

A procedure was performed in the same manner as that of Example 15-2,except that propylene carbonate (PC) was added as a solvent. Thecomposition of the solvent (PC:FEC:DEC) was 20:30:50 at a weight ratio.

Examples 15-4

A procedure was performed in the same manner as that of Example 15-3,except that 4-5-difluoro-1,3-dioxolane-2-one (DFEC) as a cyclic estercarbonate having halogen shown in Chemical formula 22 was added as asolvent. The composition of the solvent (PC:FEC:DFEC:DEC) was30:10:10:50 at a weight ratio.

Examples 15-5

A procedure was performed in the same manner as that of Example 15-3,except that DFEC was used instead of FEC as a solvent. The compositionof the solvent (PC:DFEC:DEC) was 40:10:50 at a weight ratio.

When the cycle characteristics were examined for the secondary batteriesof Examples 15-1 to 15-5, the results shown in Table 15 were obtained.

TABLE 15 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz = 3.5 μmOxygen content in the anode active material = 3 atomic % Anode activematerial layer Number of anode Discharge active material Electrolyticsolution capacity particle layers Coat Solvent (wt %) Electrolyteretention (layer) X R1 and R2 EC PC FEC DFEC DEC salt Others ratio (%)Example 4-1 24 Chemical Chemical 50 — — — 50 LiPF₆ — 90.5 Example 15-1formula 1 formula — — 50 — 50 LiPF₆ — 91.5 Example 15-2 18(1) — — 50 —50 LiPF₆ + LiBF₄ SBAH 91.6 Example 15-3 — 20 30 — 50 LiPF₆ + LiBF₄ SBAH91.8 Example 15-4 — 30 10 10 50 LiPF₆ + LiBF₄ SBAH 92.2 Example 15-5 —40 — 10 50 LiPF₆ + LiBF₄ SBAH 92.6

As shown in Table 15, in Examples 15-1 to 15-5 in which the electrolyticsolution contained other solvent (FEC or the like), other electrolytesalt (lithium tetrafluoroborate), or acid anhydride (SBAH), thedischarge capacity retention ratio was higher than that of Example 4-1in which the electrolytic solution did not contain the foregoingsubstances. In this case, when the solvent contained DFEC, the dischargecapacity retention ratio tended to be higher than that in the case inwhich the solvent contained FEC. Accordingly, it was confirmed that inthe secondary battery of the invention, the cycle characteristics wereimproved as well when the solvent composition and the electrolyte salttype were changed. It was also confirmed that when other solvent, otherelectrolyte, or the acid anhydride was added to the electrolyticsolution, the cycle characteristics were further improved. Further, itwas confirmed that when the cyclic ester carbonate having halogen shownin Chemical formula 22 was contained in the solvent, the cyclecharacteristics were improved. Furthermore, it was confirmed that as thenumber of halogen was larger, the characteristics were further improved.

Results in the case that the solvent contained the chain ester carbonatehaving halogen shown in Chemical formula 21 are not herein shown.However, the chain ester carbonate having halogen shown in Chemicalformula 21 has the same function as that of the cyclic ester carbonatehaving halogen shown in Chemical formula 22. Thus, it is evident thatwhen the solvent contained the chain ester carbonate having halogenshown in Chemical formula 21, similar results may be obtained. The sameis applied to a case that a mixture of the same/different types of theboth ester carbonates is used.

Example 16-1

A procedure was performed in the same manner as that of Example 4-1,except that the anode active material layer 54B was formed to contain ametal material together with the anode active material. When the metalmaterial was formed, the anode active material was deposited on the bothfaces of the anode current collector 54A, and then a cobalt plating filmwas grown on the both faces by electrolytic plating method. As a platingsolution, a cobalt plating solution (Nippon Kojundo Kagaku Co., Ltd.make) was used. The current density was in the range from 2 A/dm² to 5A/dm², and the plating rate was 10 nm/sec. Further, the molar ratioM2/M1 between the number of moles M1 per unit area of the anode activematerial and the number of moles M2 per unit area of the metal materialwas 1/20.

Examples 16-2 to 16-11

A procedure was performed in the same manner as that of Example 16-1,except that the molar ratio M2/M1 was 1/15 (Example 16-2), 1/10 (Example16-3), 1/5 (Example 16-4), 1/2 (Example 16-5), 1/1 (Example 16-6), 2/1(Example 16-7), 3/1 (Example 16-8), 5/1 (Example 16-9), 7/1 (Example16-10), or 8/1 (Example 16-11) instead of 1/20.

Examples 16-12 to 16-15

A procedure was performed in the same manner as that of Example 16-5,except that an iron plating solution (Example 16-12), a nickel platingsolution (Example 16-13), a zinc plating solution (Example 16-14), or acopper plating solution (Example 16-15) was used instead of the cobaltplating solution as a plating solution. The current density was in therange from 2 A/dm² to 5 A/dm² in the case of using the iron platingsolution, in the range from 2 A/dm² to 10 A/dm² in the case of using thenickel plating solution, in the range from 1 A/dm² to 3 A/dm² in thecase of using the zinc plating solution, and in the range from 2 A/dm²to 8 A/dm² in the case of using the copper plating solution. All theforegoing series of plating solutions were made by Nippon Kojundo KagakuCo., Ltd.

When the cycle characteristics of the secondary batteries of Examples16-1 to 16-15 were examined, the results shown in Table 16 and FIG. 17were obtained.

TABLE 16 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz = 3.5 μmOxygen content in the anode active material = 3 atomic % Anode activematerial layer Number of anode Discharge active material capacityparticle layers Coat Molar ratio retention (layer) Metal material X R1and R2 M2/M1 ratio (%) Example 4-1 24 — Chemical Chemical — 90.5 Example16-1 Co formula 1 formula 18(1)  1/20 90.6 Example 16-2  1/15 91.2Example 16-3  1/10 91.3 Example 16-4 1/5 91.8 Example 16-5 1/2 92.1Example 16-6 1/1 92.4 Example 16-7 2/1 92.6 Example 16-8 3/1 92.6Example 16-9 5/1 92.4 Example 16-10 7/1 91.8 Example 16-11 8/1 90.7Example 16-12 Fe 1/2 92 Example 16-13 Ni 91.9 Example 16-14 Zn 91.8Example 16-15 Cu 91.8

As shown in Table 16, in Examples 16-1 to 16-15 in which the metalmaterial was formed, the discharge capacity retention ratio was higherthan that of Example 4-1 in which the metal material was not formed. Inthis case, as shown in Table 16 and FIG. 17, as the molar ratio M2/M1became larger, the discharge capacity retention ratio tended to beincreased and decreased, and if the molar ratio M2/M1 was smaller than1/15 or larger than 7/1, the discharge capacity retention ratio tendedto be largely lowered. Further, when Examples 16-5 and 16-12 to 20-15having the different metal types were compared to each other, thedischarge capacity retention ratio tended to be higher in the case thatcobalt was used than in the case that iron, nickel, zinc, or copper wasused. Accordingly, it was confirmed that in the secondary battery of theinvention, when the metal material not reacting with the electrodereactant was formed, the cycle characteristics were improved. It wasalso confirmed that if the molar ratio was 1/15 or more and 7/1 or lessor when cobalt was used as the metal material, the characteristics werefurther improved.

Example 17-1

A procedure was performed in the same manner as that of Example 1-1,except that the fluorine resin was contained in the cathode 53 insteadof the anode 54. When the fluorine resin was contained in the cathode53, a coat containing the fluorine resin was formed on the cathodeactive material layer 53B by a procedure similar to the procedure offorming the coat 54B.

Example 17-2

A procedure was performed in the same manner as that of Example 1-1,except that the fluorine resin was contained in the separator 55 insteadof the anode 54. When the fluorine resin was contained in the separator55, a coat containing the fluorine resin was formed on the both faces ofthe separator 55 by a procedure similar to the procedure of forming thecoat 54B.

Example 17-3

A procedure was performed in the same manner as that of Example 1-1,except that the fluorine resin was contained in the electrolyticsolution instead of the anode 54. When the fluorine resin was containedin the electrolytic solution, the fluorine resin was dispersed in theelectrolytic solution while the dispersion amount was adjusted to be thesame as the content in the coat described above.

Example 17-4

A procedure was performed in the same manner as that of Examples 1-1,except that the fluorine resin was contained in both the anode 54 andthe separator 55 by a procedure similar to that of Examples 1-1 and17-2.

When the cycle characteristics of the secondary batteries of Examples17-1 to 17-14 were examined, the results shown in Table 17 wereobtained.

TABLE 17 Anode active material: silicon (electron beam evaporationmethod) Ten points average height of roughness profile Rz: 3.5 μm Oxygencontent in the anode active material: 3 atomic % Anode active materiallayer Discharge Number of anode Location containing capacity activematerial Coat fluorine resin retention layers (layer) X R1 and R2(content form) ratio (%) Example 1-1 1 Chemical formula 1 Chemicalformula 18(1) Anode (coat) 88 Example 17-1 Cathode (coat) 80 Example17-2 Separator (coat) 81 Example 17-3 Electrolytic solution 74(dispersion) Example 17-4 Anode + separator 91 Comparative 1 — — — 45example 1

As shown in Table 17, in Examples 17-1 to 17-4 in which the fluorineresin was contained in the cathode 53, the separator 55, or theelectrolytic solution or in which the fluorine resin was contained inboth the anode 54 and the separator 55, the discharge capacity retentionratio was significantly higher than that of Comparative example 1 as inExample 1-1 in which the fluorine resin was contained in the anode 54.In this case, when comparison was made among Examples 1-1 and 17-1 to17-3 having the different location containing the fluorine resin, therewas a tendency that when the fluorine resin was contained in the cathode53 or the separator 55, the discharge capacity retention ratio washigher than in the case that the fluorine resin was contained in theelectrolytic solution; and when the fluorine resin was contained in theanode 54, the discharge capacity retention ratio was still higher thanin the foregoing cases. Further, when comparison was made among Examples1-1, 17-2, and 17-4 having the different location containing thefluorine resin, there was a tendency that when the fluorine resin wascontained in both the anode 54 and the separator 55, the dischargecapacity retention ratio was higher than in the case that the fluorineresin was contained in one of the anode 54 and the separator 55.

Though no specific examples have been herein given, it is evident thatwhen the fluorine resin is contained in two or more out of the cathode53, the anode 54, the separator 55, and the electrolytic solution, thedischarge capacity retention ratio may be significantly high as well,for the reason that the discharge capacity retention ratio wassignificantly high when the fluorine resin was contained in both theanode 54 and the separator 55.

Accordingly, in the secondary battery of the invention, it was confirmedthat when the fluorine resin was contained in at least one of thecathode 53, the anode 54, the separator 55, and the electrolyticsolution, the cycle characteristics were improved. In this case, it wasalso confirmed that when the fluorine resin was contained in the anode54, the characteristics were further improved. In addition, it wasconfirmed that when the fluorine resin was contained in two or more outof the cathode 53, the anode 54, the separator 55, and the electrolyticsolution, the characteristics were further improved.

As evident by the results of the foregoing Table 1 to Table 17 and FIG.14 to FIG. 17, in the secondary battery of the invention, it wasconfirmed that when at least one selected from the group consisting offluorine resins having the structure shown in Chemical formula 1 orChemical formula 2 was contained in at least one of the cathode, theanode, the separator, and the electrolytic solution, the cyclecharacteristics were improved. Specially, it was confirmed that when theforegoing fluorine resin was contained in the anode, superior cyclecharacteristics were obtained without depending on conditions such asthe structures of the anode current collector and the anode activematerial layer, the composition of the electrolytic solution, and thetype of battery structure.

In this case, it was confirmed that when the material such as siliconand the tin cobalt alloy (material that can insert and extract lithiumand that has at least one of a metal element and a metalloid element)was used, the discharge capacity retention ratio was largely increasedthan in the case of using the carbon material such as MCMB as an anodeactive material, and thus higher effects may be obtained in the formercase. Such a result may result from the fact that when the silicon orthe like advantageous for obtaining a high capacity was used as an anodeactive material, the electrolytic solution was easily decomposed than inthe case of using the carbon material, and thus decomposition preventioneffect of the electrolytic solution was significantly demonstrated.

The invention has been described with reference to the embodiment andthe examples. However, the invention is not limited to the aspectsdescribed in the foregoing embodiment and the foregoing examples, andvarious modifications may be made. For example, in the foregoingembodiment and the foregoing examples, the descriptions have been givenof the lithium ion secondary battery in which the anode capacity isexpressed based on insertion and extraction of lithium as a batterytype. However, the battery of the invention is not always limitedthereto. The invention can be similarly applied to a secondary batteryin which the anode capacity includes the capacity associated withinsertion and extraction of lithium and the capacity associated withprecipitation and dissolution of lithium, and the anode capacity isexpressed as the sum of these capacities, by setting the charge capacityof the anode material capable of inserting and extracting lithium to asmaller value than that of the charge capacity of the cathode.

Further, in the foregoing embodiment and the foregoing examples, thedescription has been given with the specific examples of the square,cylindrical, or laminated film secondary battery as a battery structure,and with the specific example of the battery in which the batteryelement has the spirally wound structure. However, the invention can besimilarly applied to a battery having other structure such as a cointype battery and a button type battery, or a battery in which thebattery element has other structure such as a lamination structure.

Further, in the foregoing embodiment and the foregoing examples, thedescription has been given of the case using lithium as an electrodereactant. However, as an electrode reactant, other Group 1A element suchas sodium (Na) and potassium (K), a Group 2A element such as magnesium(Mg) and calcium (Ca), or other light metal such as aluminum may beused. In these cases, the anode material described in the foregoingembodiment may be used as an anode active material as well.

Further, in the foregoing embodiment and the foregoing examples,regarding the oxygen content in the anode active material in the anodeor the battery of the invention, the numerical value range thereofderived from the results of the examples has been described as theappropriate range. However, such a description does not totallyeliminate the possibility that the oxygen content may be out of theforegoing range. That is, the foregoing appropriate range is the rangeparticularly preferable for obtaining the effects of the invention.Therefore, as long as effects of the invention are obtained, the oxygencontent may be out of the foregoing range in some degrees. The same isapplied to the molar ratio M2/M1 or the like in addition to theforegoing oxygen content.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alternations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. An anode comprising: an anode current collector; an anode active material layer on the anode current collector; and a coating on the anode active material layer, wherein, the anode active material layer contains an anode active material containing at least one selected from the group consisting of a simple substance of Si, an alloy of Si, a compound of Si, a simple substance of Sn, an alloy of Sn, and a compound of Sn, ten points average height of roughness profile Rz of a surface of the anode current collector is 1.5 μm or more and 6.5 μm or less, the coating contains, except for non-perfluoropolyether resins, one or more fluorine resins each having a structure shown in Chemical formula 1 or Chemical formula 2:

OCF₂—CF₂—CF₂

_(h)

O—CF₂

_(k),  Chemical formula 1 where h and k represent a ratio, and h+k is 1; and

where m and n represent a ratio, and m+n is
 1. 2. The anode according to claim 1, wherein the fluorine resin has a structure shown in Chemical formula 3: R1-X—R2,  Chemical formula 3 where X is a structure shown in Chemical formula 1 or Chemical formula 2, and at least one of R1 and R2 is a group capable of being fixed on the surface of the anode active material layer.
 3. The anode according to claim 2, wherein at least one of R1 and R2 shown in Chemical formula 3 is a hydroxyl group, an ester group, a silane group, an alkoxysilane group, a phosphate group, an amino group, an amide group, a cyano group, or an isocyanate group.
 4. The anode according to claim 2, wherein at least one of R1 and R2 shown in Chemical formula 3 has a structure shown in Chemical formula 4:

O

_(p)

R3

_(q)

R4

_(r)R5,  Chemical formula 4 where p, q, and r are 0 or 1, R3 is a divalent linked group shown in Chemical formula 5, R4 is a divalent linked group shown in Chemical formula 6 or Chemical formula 7, and R5 is a monovalent group shown in Chemical formula 8 to Chemical formula 17:

CF₂

_(n),  Chemical formula 5 where n is one of integer numbers 1 or higher;

CH₂

_(n),  Chemical formula 6 where n is one of integer numbers 1 or higher;

O—CH₂—CH₂

_(n)OE,  Chemical formula 8 where n is one of integer numbers 0 to 10;

where R6 is a hydrogen group, an alkyl group having a carbon number of 10 or less, or —CH₂—CN;

where R7 and R8 are a hydrogen group or an alkyl group having a carbon number of 20 or less;

where R9 to R11 are a hydrogen group, a halogen group, an alkyl group having a carbon number of 10 or less, an alkylene group having a carbon number of 10 or less, or an alkoxyl group having a carbon number of 10 or less;

where R12 and R13 are a hydrogen group, a hydroxyl group, a halogen group, or an alkyl group having a carbon number of 10 or less:

where R14 and R15 are a hydrogen group or an alkyl group having a carbon number of 10 or less: —N═C═O;  Chemical formula 15

where R16 to R18 are a hydrogen group or a halogen group; and —C≡N,  Chemical formula 17
 5. The anode according to claim 1, wherein the anode active material contains oxygen, and a content of the oxygen in the anode active material is 3 atomic % or more and 40 atomic % or less.
 6. The anode according to claim 1, wherein the anode active material has an oxygen-containing region that has oxygen in the thickness direction, and a content of the oxygen in the oxygen-containing region is higher than a content of oxygen in other regions.
 7. The anode according to claim 1, wherein the anode active material has at least one metal element selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), chromium (Cr), titanium (Ti), and molybdenum (Mo).
 8. The anode according to claim 1, wherein the anode active material is composed of a plurality of particles.
 9. The anode according to claim 8, wherein the particles of the anode active material have a multilayer structure in the particles.
 10. The anode according to claim 8, wherein the anode active material is linked to the anode current collector.
 11. The anode according to claim 8, wherein the anode active material is formed by vapor-phase deposition method.
 12. The anode according to claim 9, wherein the anode active material layer has a metal material not being alloyed with an electrode reactant in a gap between the particles of the anode active material.
 13. The anode according to claim 12, wherein the anode active material layer has the metal material on an exposed face of the particles of the anode active material.
 14. The anode according to claim 12, wherein the anode active material layer has the metal material in a gap in the particles of the anode active material.
 15. The anode according to claim 12, wherein the metal material has at least one metal element selected from the group consisting of iron, cobalt, nickel, zinc (Zn), and copper (Cu).
 16. The anode according to claim 12, wherein the metal material is formed by liquid-phase deposition method.
 17. The anode according to claim 12, wherein molar ratio M2/M1 between the number of moles M1 per unit area of the anode active material and the number of moles M2 per unit area of the metal material is 1/15 or more and 7/1 or less. 